Search PubMed⌕ Search

Biomedical subjects

H Kasai

Publications and source records attributed to H Kasai.

At least 325 records · Page 18Linked to original sources
PubMed1985

Protein analyses and reagents: microscale assay of calcium-binding activity of proteins and peptides using a nitrocellulose membrane.

A simple and reliable method for the measurement of calcium binding to proteins and peptides was developed. It is composed of two procedures--filtration through a nitrocellulose membrane filter and estimation of 45Ca retained on the membrane. The routine assay was completed within a few minutes, and only microgram amounts of samples were necessary. This method permitted the quantitative determination of the calcium-binding activity of proteins and peptides including one with a molecular weight of as low as 4000. This method also permitted the detection of low-affinity interactions (Kd congruent to 10(-3) M), possibly because the nitrocellulose membrane did not show nonspecific binding of calcium and because a washing step was not employed in the routine assay. Ultrafiltration membranes when used in the apparatus gave no useful data.

Animals↗
PubMed1985

Responsiveness of Clare-Bishop neurons to visual cues associated with motion of a visual stimulus in three-dimensional space.

Photic responsiveness of cells in the medial bank of the lateral suprasylvian cortex (Clare-Bishop area) was studied using a three-dimensional visual stimulator that reproduced two visual cues (motion disparity and change in size) for perception of three-dimensional motion of a visual stimulus. About one third of them (48/148) were selectively responsive to motion disparity corresponding to approaching (AP cells, n = 30) or recessive motion (RC cells, N = 18), another half to motion of retinal images in the same direction between the two eyes corresponding to fronto-parallel motion (FP cells, n = 75), and the remaining cells were rather equally responsive to these types of stimuli (NS cells, n = 25). More than a half of the AP (19/30) or RC (11/18) cells were also responsive to increase or decrease in stimulus size, respectively, and they were optimally activated by a combination of the motion and size stimuli while relatively few FP and NS cells were sensitive to change in stimulus size. These findings indicate that the Clare-Bishop cells encode three-dimensional motion on the basis of photic responsiveness to the motion and size cues.

Animals↗
PubMed1985

Crystallization of calcium-calmodulin-trifluoperazine complex and an attempt at crystallizing calcium-free calmodulin.

Crystals suitable for X-ray structure analysis were obtained for CaM complexed with both calcium ions and a phenothiazine drug, trifluoperazine (TFP). The TFP/CaM binding ratio in crystals was experimentally determined to be nearly 1. An attempt at crystallizing calcium-free calmodulin (CaM) resulted in rigid but non-birefringent solids which exhibited no X-ray reflections.

Animals↗
PubMed1984

Detection and identification of mutagens and carcinogens as their adducts with guanosine derivatives.

For use in screening for environmental mutagens and carcinogens, a highly fluorescent derivative of guanosine, 2'-deoxy-2'-(2",3"-dihydro-2",4"-diphenyl-2"-hydroxy-3"-oxo-1"-pyrrol yl) guanosine (FG), was synthesized. When incubated with FG in aqueous solution, mutagens form adducts that can be analyzed with an HPLC-fluorescence detector-system. By this method, mutagens such as glyoxal, methylglyoxal, 2-(2-furyl)-3-(5-nitrofuryl) acrylamide and 4-nitroquinoline-N-oxide, used as model compounds, were detected rapidly with high sensitivity. Reaction with isopropylideneguanosine (IPG), followed by isolation and characterization of the mutagen-IPG-adduct was found to be a useful method for identifying unknown mutagens in crude samples. This method was successfully applied in identification of the mutagens in heated glucose (200 degrees C, 20 min); glyoxal-IPG and 8-hydroxy-IPG were identified in the reaction mixture.

Carcinogens↗
PubMed1984

Hydroxylation of deoxyguanosine at the C-8 position by ascorbic acid and other reducing agents.

The C-8 position of deoxyguanosine (dGuo) was hydroxylated by ascorbic acid in the presence of oxygen (O2) in 0.1 M phosphate buffer (pH 6.8) at 37 degrees C. Addition of hydrogen peroxide (H2O2) remarkably enhanced this hydroxylation. The Udenfriend system [ascorbic acid, FeII, ethylenediaminetetraacetic acid (EDTA) and O2] was also effective for hydroxylation of dGuo in high yield. Guanine residues in DNA were also hydroxylated by ascorbic acid. Other reducing agents, such as hydroxylamine, hydrazine, dihydroxymaleic acid, sodium bisulfite and acetol, were also effective for the hydroxylation reaction, as were metal-EDTA complexes (FeII-, SnII-, TiIII-, CuI-EDTA). An OH radical seemed to be involved in this hydroxylation reaction in most of the above hydroxylating systems, but another reaction mechanism may also be involved, particularly when dGuo is hydroxylated by ascorbic acid alone or ascorbic acid plus H2O2. The possible biological significance of the hydroxylation of guanine residues in DNA in relation to mutagenesis and carcinogenesis is discussed.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1984

Malignant parotid gland tumors and facial nerve paralysis.

During the last three decades, 586 cases of parotid gland tumor have been extirpated in our clinic. The tumors were malignant in 170 cases and, of these, facial nerve paralysis was observed at first examination in 59 patients. This paper deals with the retrospective study of these cases and is chiefly concerned with the histological types and facial nerve paralysis.

Facial Paralysis↗
PubMed1984

DNA damage induced by asbestos in the presence of hydrogen peroxide.

Treatment of calf thymus DNA with various types of asbestos fibers in the presence of hydrogen peroxide under physiological conditions (pH 7.4, 37 degrees) resulted in the hydroxylation of the C-8 position of guanine residues. DNA strand scission was also detected after these treatments.

Animals↗
PubMed1984

Formation of 8-hydroxyguanine residues in DNA by X-irradiation.

A new type of ionizing radiation-induced DNA base damage, 8-hydroxyguanine formation, was found in DNA that had been irradiated by X-rays in aqueous solution. The extent of this modification linearly increased with increase in the X-ray dose up to 40 krad. When an OH radical scavenger, ethanol, was added to the DNA solution, the hydroxylation was inhibited almost completely, suggesting that the reaction proceeds via the formation of OH radicals.

DNA↗
PubMed1983

Sympathetic ganglion neurons from aged humans grown in monolayer culture.

Sympathetic ganglia were dissected from aged patients during surgical operation done for a therapeutic purpose in the University Hospital. Nerve cells were isolated from the ganglia by trituration after incubation with collagenase, and were grown on collagen-coated plastic dishes with a growth medium. These nerve cells regenerated their axons and survived in the tissue culture for more than 3 weeks. The nerve cells tended to reduce the size in an early stage of the in vitro growth.

Aging↗
PubMed1983

Characterization and analysis of oncofetal tRNA and its possible application for cancer diagnosis and therapy.

We determined the primary structures of various tumor-specific tRNAs as well as of their normal counterparts by postlabeling RNA-sequencing procedures. The results clearly indicated that tumor-specific tRNAs are mostly formed by undermodification of hypermodified nucleosides located in the anticodon loop: no new tRNA transcripts have so far been found in tumor cells. Among the modified nucleosides affected by tumorigenesis, queuosine and Y base are the most interesting. In various tumor tRNAPhe species, hydroxy Y base located next to the anticodon is undermodified to form hypomodified hydroxy Y base lacking methyl and carboxymethyl groups. This Y base analog should be a good marker for analyzing the state of cancer cells. Queuosine, located in the first position of the anticodon, is partly or completely replaced by guanosine in all tumor cells tested so far. The amount of G-tRNA decreased markedly when the cells differentiated into mature erythroid cells, with concomitant increase of Q-tRNA. This indicates that the presence of G-tRNA is closely related to the state of the cells, not merely to the fast growth rate of tumor cells. The enzyme tRNA-guanine transglycosylase, which is a key enzyme in biosynthesis of queuosine in tRNA (inserting Q base into tRNA by a transglycosylase reaction), is active in both tumor cells and normal cells. Administration of chemically synthesized Q base to tumor-bearing mice resulted in complete conversion of G-tRNA to Q-tRNA in tumor cells, indicating that exogenously added Q base is effectively incorporated into G-tRNA. Various Q base analogs that can be used as substrates for tRNA-guanine transglycosylase were synthesized chemically. These compounds may be used for clinical cancer diagnosis, since they should be incorporated selectively into tRNA in tumor cells. In addition to use as cancer chemotherapeutic reagents, it should be possible to develop new Q base analogs that induce miscoding or blocking of protein synthesis after insertion into G-tRNA.

Animals↗
PubMed1983

Comparative study of prostaglandin I2 (PG I2) and thromboxane A2 (TXA2) synthetase inhibitor (OKY-1581) on hemodynamics in pregnant dogs.

Effects of intravenous injections of prostaglandin I2 (PG I2) and thromboxane A2 (TXA2) synthetase inhibitor (OKY-1581) on mean arterial pressure (MAP), cardiac output (CO), heart rate (HR), renal blood flow (RBF), and uterine blood flow (UBF) were investigated in the anesthetized pregnant dog. A dose-dependent fall in MAP was observed with these two agents. HR was almost unchanged by both PG I2 and TXA2 synthetase inhibitor. PG I2 and TXA2 synthetase inhibitor produced increases in CO and RBF in a dose-dependent manner. PG I2 caused a dose-dependent decrease in UBF, while TXA2 synthetase inhibitor was followed by an insignificant decrease in UBF. PG I2 and TXA2 synthetase inhibitor did not induce any increase in intrauterine pressure (IUP). The possibility of treatment of pregnancy-induced hypertension with PG I2 or TXA2 synthetase inhibitor is discussed.

Acrylates↗
PubMed1983

Hydroxylation of the C-8 position of deoxyguanosine by reducing agents in the presence of oxygen.

The C-8 position of deoxyguanosine was hydroxylated by various reducing agents in the presence of oxygen in 0.1 M phosphate buffer (pH 6.8) at 37 degrees C. As reducing agents, ascorbic acid, hydroxylamine, hydrazine, sodium bisulfite and dihydroxymaleic acid were used. Metal powder (Fe, Ni) or metalethylenediaminetetraacetic acid (EDTA) complex (FeII-EDTA, TiIII-EDTA) was also effective for the hydroxylation reaction in the presence of oxygen. Guanine residues in calf thymus DNA were also modified by these reagents. The possible biological significance of the hydroxylation of guanine residue in DNA in relation to mutagenesis and carcinogenesis is discussed.

Ascorbic Acid↗
PubMed1982

DNA-binding of IQ, Me-IQ and Me-IQx, strong mutagens found in broiled foods.

Non-covalent DNA-binding has been studied of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (Me-IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (Me-IQx), strong mutagens found in broiled foods. These mutagens are intercalated into DNA, as found by ultraviolet absorption and gel electrophoresis. The binding of IQ is stronger with GC pairs than AT pairs in DNA. The binding constants with calf thymus DNA are 1.6 X 10(6) (Me-IQ), 0.9 X 10(6) (IQ) and 0.7 X 10(6) M-1 (Me-IQx) at pH 6.0. This order of DNA affinity agrees with the order of mutagenicity towards Salmonella typhimurium TA98.

Animals↗
PubMed1982

Mutagenicity of methylglyoxal in coffee.

Major carbonyl compounds from a extract of ground roasted coffee beans were identified as 5-hydroxymethylfurfural, acetol, glyoxal, methylglyoxal and diacetyl. Among these carbonyl compounds, methylglyoxal showed considerable mutagenic activity toward Salmonella typhimurium TA100 without S9 mix (around 100,000 revertants/mg). More than 50% of the total mutagenic activity of coffee can be accounted for by the activity of methylglyoxal.

Aldehydes↗