Search PubMed⌕ Search

Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 1,045 records · Page 58Linked to original sources
PubMed1990

Precision determination and Adair scheme analysis of oxygen equilibrium curves of concentrated hemoglobin solution. A strict examination of Adair constant evaluation methods.

To examine the validity of the recent finding by Gill et al. (S.J. Gill, E. Di Cera, M.L. Doyle, G.A. Bishop and C.H. Robert, Biochemistry 26 (1987) 3995) that the third overall Adair constant (A3) for human hemoglobin tetramers (Hb A) is too small to be determined and therefore that the contribution of the triply ligated species in the oxygenation process is negligibly small, highly accurate oxygen equilibrium curves for concentrated pure Hb A solutions were determined with an automatic oxygenation apparatus and analyzed by a least-squares curve-fitting method with various options. The present results indicate that an appropriate choice of weighting for data points is the key to the correct evaluation of the Adair constants and the present experimental data cannot accommodate the Adair scheme with A3 = 0, giving distinctly positive values for A3. Several criteria for correct determination of the Adair constants are presented.

Hemoglobins↗
PubMed1990

Comparative least-squares analysis of hemoglobin oxygen equilibrium curves.

The oxygen-binding properties of hemoglobin have been studied at 600 microM protein concentration with organic phosphate, and analyzed by a series of different nonlinear least-squares analysis methods to determine whether reports of negligibly small values of the third overall Adair parameter, A3, are consequences of the data or a product of the data analysis. Data from other laboratories were analyzed as well. The single most important factor in creating a measurement that yields a small A3 is the use of equally weighted fitting in the Adair equation, while end-weighted fitting generally yields a larger A3. Endpoint extrapolation is ruled out as a major cause of abnormal A3 values. Monte Carlo simulations of the 600 microM results suggest that, if a small A3 were present, end weighting is at least as sensitive to a small A3 as equal weighting. We conclude that equally weighted fitting of the tetrameric Adair equation is unable to resolve the upper asymptote of the oxygen-binding data, resulting in an unusually small value for A3.

Hemoglobin A↗
PubMed1990

Sensitive assay system for bile acids and steroids having hydroxyl groups utilizing high-performance liquid chromatography with peroxyoxalate chemiluminescence detection.

3 alpha- or 3 beta-hydroxysteroids, such as bile acids (free and glycine and taurine conjugates), 3 beta-hydoxy-5-cholenic acid, pregnanediol, 5-pregnene-3 beta, 20 beta-diol and 5-pregnene-3-beta,20 alpha-diol, were converted to 3-oxosteroids by enzymatic reaction using immobilized hydroxysteroid dehydrogenase, derivatized with dansylhydrazine to the corresponding dansyl hydrazones and purified by gel permeation chromatography. The dansyl hydrazones were chromatographed on a C18 column with a tetrahydrofuran-containing eluent and detected at the level of a few femtomoles by a peroxyoxalate chemiluminescence post-column reaction using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate as a chemilumigenic reagent. The dansyl hydrazones of chenodeoxycholic acid and deoxycholic acid (free and glycine and taurine conjugates) in particular, which coeluted under the chromatographic conditions above, were separated using an eluent including acetonitrile and 2,6-di-O-methyl-beta-cyclodextrin and detected in the same way.

Bile Acids and Salts↗
PubMed1990

Activation of single Ca2(+)-dependent K+ channel by external ATP in mouse macrophages.

Single Ca2(+)-dependent K+ currents responding to external ATP were recorded from cell-attached patches on mouse peritoneal macrophages. Extracellularly applied ATP activated an inward single-channel current with a conductance of 25 pS and a reversal potential of -79 mV (pipette potential, Vp) when the pipette contained a 145 mM KCl solution. The reversal potential was shifted 56 mV positive by a 10-fold reduction in external (pipette) K+ concentration. The effect of ATP was abolished by either removal of external Ca2+ or treatment with an intracellular Ca2+ chelator, the acetoxymethyl ester of 1,2-bis (2-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid (BAPTA-AM). This channel has a mean open time of 9.1 ms and open probability was not strongly dependent on Vp in the range tested (+120 to -30 mV).

Adenosine Triphosphate↗
PubMed1990

[A study of the androgenic activity of anti-androgen].

To investigate the androgenic activity of steroidal and nonsteroidal anti-androgens, the effect of several compounds on some parameters as an androgenic activity was measured in the ventral prostate (VP) and seminal vesicle gland (SV) of castrated male rats. Ornithine decarboxylase (ODC) activity, arginase activity, androgen receptor (AR) in cytosol and nucleus, histological examination and weight of accessory sex organs were used as parameters for androgenic activity. The ventral prostate weight was increased by the administration of not only steroidal anti-androgen, medroxyprogesterone (MPA), chlormadinone acetate (CMA) and cyproterone acetate (CPA), but also estradiol-17 beta(E2) and nonsteroidal anti-androgen, AA 560. However flutamide (Flu) failed to increase VP weight. In SV, the tendency to increase weight by the administration of these compounds was also observed. However, it was not obvious as in VP. It was proven by the measurement of the parameters that all tested compounds except Flu had an androgenic activity. It seems that the androgenic activity was caused by a different mechanism because the parameter response to the administrated compounds was not identical.

Androgen Antagonists↗
PubMed1990

Transcription of biliary glycoprotein I gene in malignant and non-malignant human liver tissues.

Biliary glycoprotein I (BGP I) is a member of carcinoembryonic antigen (CEA) gene family consisting of at least 11 related genes. The transcription of BGP I gene was analysed in malignant and non-malignant human liver tissues with a 396-bp 3'-untranslated region probe from a cDNA clone 4-13 which was newly isolated from an adult human colon cDNA library. Among 21 tissue samples from 14 patients with hepatocellular carcinoma, 16 samples were clearly shown to express a single 3.9-kb message. This message was also found in the hepatoma cell line HuH-7. When the malignant tissues were compared to the non-malignant ones for the intensity of the band, no significant difference was observed. mRNAs of CEA and non-specific cross-reacting antigen (NCA) were not detected in 5 samples which were shown to have the message of the BGP I gene. These data suggest that the human hepatocyte and its malignant transformant produce BGP I, and that this could correspond to the cross-reacting antigen previously detected in the liver.

Antigens, CD↗
PubMed1990

Identification of genetically high risk individuals to lung cancer by DNA polymorphisms of the cytochrome P450IA1 gene.

A good correlation was observed between enhanced lung cancer risk and restriction fragment length polymorphisms (RFLPs) of the P450IA1 gene with the restriction enzyme MspI. Genotype frequencies of 0.49 for the predominant homozygote, 0.40 for the heterozygote, and 0.11 for the homozygous rare allele were observed in a healthy population. Among lung cancer patients, the frequency of homozygous rare allele of P450IA1 gene was found to be about 3-fold higher than that among healthy population, and this difference was statistically significant. This is the first report to identify the genetically high risk individuals to lung cancer at the gene level.

Adult↗
PubMed1990

Studies on the effects of imidazole on the peroxyoxalate chemiluminescence detection system for high performance liquid chromatography.

The catalytic effect of bases (imidazole, pyridine, Tris and triethylamine) on the peroxyoxalate chemiluminescence (PO-CL) reaction for high performance liquid chromatography (HPLC) was investigated. Imidazole increased PO-CL intensity extraordinarily, whereas the other bases (pyridine, Tris and triethylamine) did not. The peak heights of dipyridamole (coronary vasodilator) obtained using the eluents containing buffers were largest at pH 7.0, a few times less at pH 6.0 and pH 5.0, 100 times less at pH 4.0 and a few hundred times less at pH 3.0. The eluents containing buffers at pH 3, 4, 5, 6 or 7 each with imidazole increased the peak heights by a few to ten times as compared with those without imidazole, and those peak heights were within one order of magnitude. On the other hand, the eluent containing buffer at pH 2 did not affect the peak heights with or without imidazole. Bis(4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl) oxalate (TDPO) alone and bis(2,4-dinitrophenyl)oxalate (DNPO) plus TDPO were recommended to be used against eluents containing buffers of pH 5-7 and pH 3-4, respectively. Dipyridamole and benzydamine hydrochloride (anti-inflammatory drug) were separated on the ODS column and detected by the present system. The detection limits of dipyridamole and benzydamine hydrochloride were 40 amol and 270 fmol, respectively.

Chromatography, High Pressure Liquid↗
PubMed1990

Evaluation of pyrimido[5,4-d]pyrimidine derivatives as peroxyoxalate chemiluminescence reagents using a flow injection system.

Eighteen kinds of pyrimido[5,4-d]pyrimidines together with several commercially available fluorescent compounds such as perylene, Rhodamine B, etc., were evaluated as the reagents for a peroxyoxalate chemiluminescence (CL) detection system by using a flow injection method. The peroxyoxalate CL reaction employed consists of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide, triethylamine, and a fluorophore. Under the conditions used, 2,6-bis[di-(2-hydroxyethyl)amino]-4,8- dipiperidinopyrimido[5,4-d]pyrimidine (Dipyridamole) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (1i) gave very intense chemiluminescence intensities which were larger than those of any other commercially available fluorescent compounds tested (e.g., 10 times larger than that of perylene).

Chromatography, High Pressure Liquid↗
PubMed1990

Determination of fluorescent cyanobenz[f]isoindole derivatives of dopamine and norepinephrine using high performance liquid chromatography with chemiluminescence detection.

Dopamine (DA), norepinephrine (NE) and 3,4-dihydroxybenzylamine (DHBA) are converted to highly fluorescent cyanobenz[f]isoindole (CBI) derivatives by reacting these amines with naphthalene-2,3-dicarboxaldehyde in the presence of cyanide ion. Femtomole amounts of these CBI derivatives separated by reverse-phase high performance liquid chromatography can be detected by a post-column chemiluminescence system utilizing bis(2,4-dinitrophenyl) oxalate and hydrogen peroxide. Linear detection response was observed between 1 to 600 fmol, giving a signal to noise ratio of approximately 15 at the 1 fmol level. An assay procedure was developed for the determination of DA and NE in 20 microL of urine sample using DHBA as the internal standard.

Animals↗
PubMed1990

A new method for the high performance liquid chromatographic determination of TA-870, a dopamine prodrug (catechol ester compound).

A new method for the high performance liquid chromatographic (HPLC) determination of N-(N-acetyl-L-methionyl)-O,O-bis(ethoxycarbonyl)dopamine (TA-870), a dopamine prodrug, in biological fluid has been developed. In order to measure with an electrochemical detector (ECD), TA-870 was passed first through an immobilized carboxylesterase column to be converted to the electrochemically active deethoxycarbonylated TA-870 (DEC-TA-870). The properties of this carboxylesterase immobilized on Sepharose 4B were examined by this flow injection system. Hydrolysis of TA-870 with this immobilized carboxylesterase was a maximum at pH 7-8 and 50 degrees C, and the activity decreased in the presence of organic solvent such as acetonitrile. For the determination of TA-870 in biological fluids, an HPLC-immobilized enzyme-ECD system using a column-switching technique was developed. The blood was deproteinized with ethanol, and TA-870 in the ethanol extracts was adsorbed in Bond Elut C18. The dichloromethane eluate from Bond Elut C18 was injected into the HPLC system. The HPLC apparatus was composed of three pumps, two separation columns (LiChrosorb Si 60 and mu Bondasphere), a trap column (Bond Elut), an enzyme column, ECD and the column-switching system. The calibration curve for TA-870 in blood was linear in the range from 2 to 200 ng/mL. This new assay method might be useful also for the determination of other catechol ester compounds.

Animals↗
PubMed1990

Thermodynamic study of phase transfer of precipitates on SiC whisker reinforced glass ceramics.

Physiochemical properties of glass ceramics in weakly buffered, supersaturated, metastable calcium and phosphate solution were studied. Formations of calcium phosphate precipitates were also analyzed thermodynamically. All biomaterials examined here showed primarily dissolution process and subsequent nucleation. Dissolution was enhanced in those which contained Na2O and/or SiC. The dissolution of calcium and phosphate ions from biomaterials and subsequent nucleation of calcium phosphate salts after induction time resulted in a stable equilibrium having solubility characteristics similar to octacalcium phosphate (OCP). The most soluble material, CPSN-SiC, showed an initial transient equilibrium with amorphous calcium phosphate (ACP). From above results, calcium phosphate ceramics had certain driving force of its own which kept the equilibrium of solution to OCP thermodynamically for 7 days. Despite the favorable solubility equilibrium attained, there still remain problems for clinical application.

Biocompatible Materials↗
PubMed1990

Sequential polydepsipeptides as biodegradable carriers for drug delivery systems.

Sequential polydepsipeptides containing both peptide and ester bonds, poly[(L-alanyl)n-gamma-ethyl L-glutamyl-L-lactyl] (n = 0, 1, 2, and 3) (poly[(Ala)n-Glu(OEt)-Lac]), were prepared for application as biodegradable carriers for drug delivery systems. The in vivo degradation of these polymers was evaluated by subcutaneous implantation in the backs of male rats, and was strongly influenced by the number (n) of Ala units in poly[(Ala)n-Glu(OEt)-Lac]. The resulting poly(Ala-Ala-Glu(OEt)-Lac) gave the highest degradability, in which 100% degradation was observed 24 weeks from the start of implantation. A luteinizing-hormone-releasing hormone agonist des-Gly10-[D-Leu6]-LH-RH ethylamide (LH-RH agonist), was incorporated into a sequential poly(Ala-Ala-Glu(OEt)-Lac) carrier by the melt-pressing technique, which gave fine cylindrical polymer formulations with different structures of drug dispersion, e.g., blend-type and sandwich-type formulations. The rate of in vivo release of LH-RH agonist from a blend-type formulation showed a linear decrease with time until its release was finished after 6 weeks' implantation. In contrast, in a sandwich-type formulation, the in vivo release rate was apparently maintained constant over a period of 16 weeks (24 +/- 14 micrograms/day).

Amino Acid Sequence↗
PubMed1990

Significance of adenocarcinoma-associated antigen YH206 levels in the pancreatic juice.

We measured the pancreatic juice levels of antigen YH206, which is a new tumor marker of adenocarcinomas detected by monoclonal antibody YH206 (Hinoda et al., Int. J Cancer 24(5):653-658, 1988). Sandwich enzyme immunoassay revealed that samples from patients with pancreas cancer (n = 21) showed significantly higher values (P less than 0.01) than those of healthy controls (n = 15). Eight out of 21 (38.1%) samples from patients with pancreas cancer showed more than 100 U/ml, whereas only one out of 20 (5.0%) from patients with chronic pancreatitis exhibited more than 100 U/ml of antigen YH206. Simultaneous measurement of antigen YH206 and CA19-9 demonstrated that although a higher incidence of positivity in the case of pancreas cancer was obtained for both antigens, antigen YH206 showed much lower incidence of positivity (14%) than CA19-9 (57%) in patients with chronic pancreatitis. Therefore, the measurement of antigen YH206 in the pancreatic juice could be of use for the diagnosis of pancreas cancer.

Adenocarcinoma↗
PubMed1990

Reconstruction of palate with radial forearm flap; a report of 3 cases.

A prosthesis is the preferred method for the closure of a palatal defect following maxillectomy, with fairly satisfactory results. However, some patients suffer from symptoms due to mismatch of the prosthesis. We have reconstructed palatal defects using radial forearm flaps in 3 cases. The forearm flap is utilised for palatal reconstruction in the double-folded form. The flap is thin and pliable, there are no problems in regard to bulk and drooping of the flap, and the patients can wear the denture with minimal discomfort. We believe that reconstruction of the palate with a forearm flap is a useful procedure, especially for patients suffering from symptoms due to mismatch of the prosthesis.

Female↗
PubMed1990

Reconstruction of penis with free deltoid flap.

Two cases of reconstruction of the penis with a free deltoid flap are described. The urethra was reconstructed with part of the flap and external coverage of the penis was provided with the remainder. In one case an autogenous rib cartilage graft was inserted in the reconstructed penis as a strut. Postoperatively both patients can urinate standing up, and for the one in which a rib cartilage graft was used sexual intercourse is possible. Both cases have good recovery of tactile and protective sensation in their reconstructed penis.

Adult↗