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Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 1,513 records · Page 84Linked to original sources
PubMed1979

Influence of steric factors on oxygen binding. I. Studies on 2,4-diisopropyldeuteroheme-myoglobin.

Sperm whale apomyoglobin was recombined with 2,4-diisopropyldeuterohemin to form 2,4-diisopropyldeuteroheme-myoglobin and its various physico-chemical properties were investigated to get an insight into the structural and functional role of the peripheral vinyl groups. 2,4-Diisopropyldeuteroheme-myoglobin showed a four times lower oxygen affinity at 25 degrees C and larger enthalpy and entropy changes of oxygenation than the corresponding values of native myoglobin. 2,4-Diisopropyldeuteroheme-metmyoglobin shows a pKa value of 9.68 which is higher than those of native metmyoglobin and mesoheme-metmyoglobin. The rate of autooxidation of oxy-form was about seven times larger in 2,4-diisopropyldeuteroheme-myoglobin than in native myoglobin. The electron-donating effect of isopropyl groups does not give straightforward explanation for these anomalous properties of 2,4-diisopropyldeuteroheme-myoglobin. It is proposed that site and stereospecific van der Waals' interaction between the polypeptide side chains and the peripheral 2,4-diisopropyl groups may weaken the interaction between the bound oxygen molecule and the distal His, resulting in the decrease in the stability of oxyform.

Animals↗
PubMed1979

Stoichiometry of the reaction of oxyhemoglobin with nitrite.

During the reaction of oxyhemoglobin (HbO2) with nitrite, the concentration of residual nitrite, nitrate, oxygen, and methemoglobin (Hb+) was determined successively. The results obtained at various pH values indicate the following stoichiometry for the overall reaction: 4HbO2 + 4NO2- 4H+ leads to 4Hb+ + 4NO3- + O2 + 2H2 O (Hb denotes hemoglobin monomer). NO2- binds with methemoglobin noncooperatively with a binding constant of 340 M-1 at pH 7.4 and 25 degrees C. Thus, the major part of Hb+ produced is aquomethemoglobin, not methemoglobin nitrite, when less than 2 equivalents of nitrite is used for the oxidation.

Hemoglobin A↗
PubMed1979

Biosynthesis of ribosomal proteins by poly(A)-containing mRNAs from rat liver in a wheat germ cell-free system and sizes of mRNAs coding ribosomal proteins.

(1) Poly(A)-containing mRNAs from total polysomal RNA of regenerating rat liver were incubated with [3H]leucine in a wheat germ cell-free system. Ribosomal proteins were purified as described previously [1], and with two-dimensional gel electrophoresis. The proteins on the gel except for less basic protein had appreciable radioactivity, whereas the surrounding areas had very low radioactivity. Acetic acid-soluble proteins labeled in this system were subjected to three-dimensional gel electrophoresis [2]. Except for L1 and L2 proteins, each of the ribosomal proteins, including less basic ones, showed a major radioactive peak coinciding with the protein band on SDS gel. Thus, the wheat germ cell-free system completely translates almost all mRNAs for individual ribosomal proteins. Equimolar amounts of almost all ribosomal proteins were synthesized in the presence of the saturating concentration of mRNAs. (2) Free polysomes from regenerating rat liver were fractionated into three sizes. Each class of polysomes was incubated with [3H]leucine. Ribosomal proteins with molecular weights of 40 000 to 21 000 were mainly synthesized by Fraction B (5-14 monomeric ribosomes), L1 and L2 [2] with 60 000 and 54 000, by Fraction C (greater than 15 monomeric ribosomes) and B, and ribosomal proteins smaller than 20 000 by Fractions A (less than pentamer) and B. (3) mRNAs from rat liver total polysomes were fractionated into seven classes by size and each was translated in the wheat germ extract. Ribosomal proteins with molecular weights of 54 000 to 30 000 were mainly synthesized by mRNAs of 12 to 14.5 S, ribosomal proteins of 35 000 to 22 000 by those of 9.5 to 12 S, ribosomal proteins of 22 000 to 13 000 by those of 7 to 9.5 S, and smaller ribosomal proteins by those smaller than 7 S. These results indicate that individual ribosomal proteins are synthesized by monocistronic mRNAs, the lengths of which are proportional to the molecular weights of the corresponding ribosomal proteins.

Animals↗
PubMed1979

Evidence for dissociation of ferrihemoglobin by poly-L-lysine.

Circular dichroism and absorption spectra of ferrihemoglobin were shown to be altered upon binding with poly-L-lysine at alkaline pH. When ferrihemoglobin immobilized to Sepharose gel was treated with poly-L-lysine, hemoglobin subunits were released from the gel. These results suggest that ferrihemoglobin was dissociated into subunits by poly-L-lysine.

Circular Dichroism↗
PubMed1979

High-performance liquid chromatographic determination of dopamine sulfoconjugates in urine after L-dopa administration.

A procedure was developed for the separation and determination of dopamine-3-O-sulfate (DM-3-S) and dopamine-4-O-sulfate (DM-4-S) in the urine of subjects administered L-DOPA. The method consists of sample preparation using cation- and anion-exchange resins followed by determination of the sulfates by high-performance liquid chromatography. The addition recoveries were 96 +/- 2.9% (S.D.) for DM-3-S and 93 +/- 3.0% (S.D.) for DM-4-S. Twenty samples could be measured per day. When every 2-h urine specimen from normal subjects was analyzed after L-DOPA administration (0.5 g), the maximum excretion of each sulfate was observed in the second 2-h specimen. For the first 6 h 7.5 +/- 1.5% (S.D.) of the administered L-DOPA was excreted as DM-O-sulfates. During this time, the ratio of DM-4-S to the DM-O-sulfates was 11.7 +/- 0.58% (S.D.).

Adult↗
PubMed1979

An experimental study on histamine H2-receptor antagonist on calcium, gastrin and histamine induced gastric acid secretion in rat.

The suppressive effect of histamine H2-receptor antagonist, cimetidine, on gastric secretion was investigated in Ghosh-Schild rat. The study above was done in basal state under infusing normal saline (1 ml/h) and stimulated state by histamine-di-chloride (3.5 mg/kg-h), tetragastrin (50 mcg/kg-h) or calcium chloride (4 mg/kg-h). Dose related increase of cimetidine (1.7, 3.5, 7.0 and 14.0 mg/kg-h) were observed and correlated with the degree of inhibition of acid secretion. Cimetidine had a potent inhibitory activity on either basal and stimulated acid output by the agents above. Basal acid secretion was completely abolished by 3.5 mg/kg-h of cimetidine to the level of anacidity. The degree of inhibition by the same dose of cimetidine was different among the agents used as stimulant on acid secretion and it followed in the order of calcium, gastrin and histamine subsequently. This study indicated that histamine H2-receptor participated the gastric secretion induced by either gastrin or calcium other than histamine itself. This fact indicated the important role of endogenous histamine in gastric secretion induced by calcium and gastrin.

Animals↗
PubMed1979

Clinical and radiographic study of dens invaginatus.

After a determination of the frequency of dens invaginatus by means of radiographic observations, various problems of its identification are discussed. The 188 teeth showing a distinct loop-shaped invagination apically on the radiograph were studied for the presence or absence of caries and periapical lesions. It was demonstrated that periapical lesions caused by caries are mostly due to interproximal caries and that the frequency of periapical lesions caused by caries in the dens invaginatus area was less than previously reported. Comments are made on the dens invaginatus cases having periapical lesions without caries and the parameters for future studies.

Adult↗
PubMed1979

Studies on the protein components of 110S and total ribonucleoprotein particles of rat liver nucleoli.

Proteins of rat liver nucleolar RNP, especially 110S RNP containing 45S RNA, were investigated and the following results were obtained. 1. Nucleolar extract was prepared from thioacetamide-treated rat liver nucleoli in the presence of 1 mg PVS per ml. Sucrose-density gradient centrifugation of the nucleolar extract showed RNP distributed between 60S and 110S. The 110S particles (110S RNP) contain 45S RNA as judged from the radioactivity profiles of nucleolar extract labelled in vivo with [3H]orotic acid for 10 min and 2 h. The protein components of 110S RNP and total RNP heavier than 60S (total RNP) were analyzed and compared. 2. Since the effects of PVS treatment on the extraction and the electrophoretic pattern of ribosomal proteins were removed by increasing the Mg2+ concentration during acetic acid extraction, as described in our preceding paper (1), proteins of 110S RNP as well as total RNP from PVS-pretreated nucleoli were extracted with 67% acetic acid containing 334 mM Mg2+ and analyzed by two-dimensional acrylamide gel electrophoresis. Ribosomal proteins masked by contaminating histone spots on the gel were identified by SDS-acrylamide gel electrophoresis. 3. 110S RNP contained a large portion of ribosomal proteins from large subunits; 24 protein spots were distinct, 6 protein spots were faint and 5 proteins (L3, L8, L30, L35, and L36) were missing completely. On the other hand, 110S RNP contained a small number of small subunit proteins; only 6 proteins showed distinct spots, 7 proteins showed faint spots and 12 protein spots were missing. 110S particles contained 11 non-ribosomal proteins, although it is difficult to rule out the possibility that some of them were contaminating chromatin proteins. 4. Total RNP showed electrophoretic patterns of 60S ribosomal proteins similar to those of 110S RNP, although L3 protein was present as a faint spot and 26 proteins showed distinct spots. Total RNP contained more small subunit proteins than 110S RNP; 7 proteins spots were distinct, 10 protein spots were faint and 8 protein spots were missing. The results suggest that some kinds of 40S proteins and L3 protein are attached to 110S RNP during the processing of 110S RNP.

Animals↗
PubMed1979

The linkage between the four-step binding of oxygen and the binding of heterotropic anionic ligands in hemoglobin.

The linkage between the four-step binding of oxygen and the binding of heterotropic anionic ligands in hemoglobin was investigated by accurately measuring and analyzing the oxygen equilibrium curves of human adult hemoglobin in the presence and absence of various concentrations of one or two of the following materials: chloride (Cl-), 2,3-diphosphoglycerate (DPG), and inositol hexaphosphate (IHP). Each equilibrium curve was analyzed according to the Adair equation to evaluate the four-step oxygen equilibrium constants (Adair constants) and the median oxygen pressure. The binding constants of the anions for the molecular species of hemoglobin carrying j oxygen molecules, Hb(O2)j(j=0,1,...,4), were evaluated from the dependences of the Adair constants and the median oxygen pressure on the anion concentration by introducing a model which takes the competitive binding of Cl- and DPG or IHP into account. Assumptions made in the model are: (a) the hemoglobin molecule has two oxygen-linked binding sites for Cl- which are equivalent and independent and (b) no Cl- can be bound to hemoglobin to which DPG or IHP is already bound and vice versa. Thus, we could obtain values for the intrinsic binding constants of Cl- and DPG, i.e., the constants in the absence of other competitive anions. For IHP, only the binding constants and apparent binding constants for Hb and Hb(O2)2 were obtained. Values of the Cl- binding constants and apparent binding constants for DPG and IHP, i.e., the binding constants in the presence of Cl- for Hb and Hb(O2)4, were in reasonable agreement with literature values. From the binding constants we calculated anion binding curves for Hb(O2)j(J=0,1,...,4), the number of anions bound to Hb(O2)J, And the relationship between fractional anion saturation of hemoglobin and fractional oxygen saturation. The numbers of released anions are not uniform with respect to oxygenation step. This non-uniformity is the reason for the changes in the shape of the oxygen equilibrium curve with anion concentration changes and for the non-uniform dependences of the Adair constants on anion concentration, and also results in non-linear relations between anion saturation and oxygen saturation. The anion binding constants and various binding properties of the anions derived from those constants are consistent with those observed by other investigators using different techniques, indicating that the present model describes the oxygen-linked competitive anion binding well.

Adult↗
PubMed1979

Effects of antiprostatic agents on 5alpha-dihydrotestosterone binding to rat hypophyseal and hypothalamic cytosol macromolecules.

The binding of 5alpha-dihydrotestosterone to the hypophyseal and hypothalamic cytosol macromolecules prepared from castrated male rats was observed. The effects of antiprostatic agents on 5alpha-dihydrotestosterone binding to both hypophyseal and hypothalamic cytosol macromolecules was examined. Cyproterone acetate and chlormadionone acetate showed the significant inhibiting effects on 5alpha-dihydrotestosterone binding to 7-8 S macromolecules of cytosol from both hypophysis and hypothalamus. SCH 13521 and AA 560 did also affect 5alpha-dihydrotestosterone binding to 7-8 S macromolecules of cytosol from both tissues.

Androgen Antagonists↗
PubMed1979

Application of an automatic oxygenation technique to analysis of oxygen equilibrium curves for hemoglobinopathic red cells and functional screening of clinically important hemoglobinopathies.

The automatic oxygenation technique of Imai et al (Biochimica Biophysica Acta, 200:189--196, 1970) was slightly modified and applied to the study of oxygen equilibrium curves of dilute, red-cell suspensions from normal subjects and individuals with hemoglobinopathies, enzymopathies, and other hematologic disorders. The p50 values of non-smoking, normal adults were 25.9 +/- 0.6 mm Hg at pH 7.4 and 37 degrees C, and corresponded to the values for whole blood reported in the literature. The oxygen equilibrium curves of suspensions from subjects with enzymopathies revealed shifts in position which are thought to be due to alterations in the concentration of 2,3-DPG of the red cells. Abnormalities in shape of the equilibrium curves were observed only for the hemoglobinopathic red cells, and could best be illustrated by the abnormally low Hill's exponent (n*). Analyses of the n* values of 34 patients with various red-cell disorders of unknown causes led to the identification of ten cases showing low values. In five of the ten patients, the presence of an abnormal hemoglobin was confirmed using column chromatography on Amberlite CG--50. These results point to the usefulness of the Hill Plot analysis of red-cell oxygen dissociation curves in functional screening for clinically important hemoglobinopathies.

Erythrocytes↗