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Biomedical subjects

M Tsuda

Publications and source records attributed to M Tsuda.

At least 541 records · Page 30Linked to original sources
PubMed1984

Effect of salt on photocycle and ion-pumping of halorhodopsin and third rhodopsinlike pigment of Halobacterium halobium.

The cytoplasmic membranes of Halobacterium halobium contain at least three retinal pigments: bacteriorhodopsin (bR), halorhodopsin (hR), and a third rhodopsinlike pigment (tR). The amplitudes of the phototransient in the photolysis of hR and tR were measured in various salt solutions. Halogen ion (except fluoride) was required to retain the photocycle of hR. Parallels between the amplitude of the phototransient of hR and the magnitude of the photo-induced tetraphenylphosphonium (TPP+) uptake suggests that hR is a light-driven halogen pump, which supports the hypothesis by Schobert and Lanyi (J. Biol. Chem., 1982, 257:10306-10313). The order of effectiveness of halogen was Br- greater than Cl- greater than I-. On the other hand, no specific ion was required to retain the photocycle of tR, and tR was concluded to be nonelectrogenic.

Anions↗
PubMed1984

Total body irradiation as a method of preparation for bone marrow transplantation: a new technique and review.

Recently total body irradiation has been used as a method of preparation for the bone marrow transplantation. However, it has become apparent that total body irradiation is one of the causes of interstitial pneumonia. There are several factors in total body irradiation that may induce interstitial pneumonia. 1) Total dose. Usually 10 Gy which is used in America, reduces the survival of the leukemic cells to about 0.001% while the normal tissue cells are reduced to about 1%. However there is no evidence that 10 Gy is enough for bone marrow transplantation. 2) Dose rate. A dose of 10 Gy given at a high dose rate is about 10 times more effective than at a low dose rate. However, the dose-rate effects become less pronounced when the single dose is under 2 Gy. 3) Dose fractionation. The effect on cell survival of dose fractionation is discussed. Since the recovery from the radiation damage is usually greater in normal cells than in the malignant cells, fractionated radiation will have great advantages. 4) Dose distribution and new irradiation technique. It is difficult to obtain homogeneous distribution if a single large radiation field is used. In our hospital the patients receive total body irradiation by a moving treatment couch method under X-rays exposure. Homogeneous dose distribution is achieved with this method. Total body irradiation will become an almost routine treatment method for bone marrow transplantation with multifractionated irradiation.

Bone Marrow Transplantation↗
PubMed1984

Presence of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acids and tyramine as precursors of mutagens in soya sauce after nitrite treatment.

Soya sauce showed marked direct-acting mutagenicity toward Salmonella typhimurium TA 100 after nitrite treatment. Three precursors showing mutagenicity after nitrite treatment were isolated from soya sauce. Their structures were determined to be (-)-(1S,3S)-1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid [(-)-(1S,3S)-MTCA], its stereoisomer (-)-(1R,3S)-MTCA and tyramine. The numbers of revertants of TA 100 induced by 1 mg each of (-)-(1S,3S)-MTCA, (-)-(1R,3S)-MTCA and tyramine, after nitrite treatment, were 17 400, 13 000 and 3 900, respectively, without S9 mix. The amounts of MTCA isomers and tyramine in various Japanese soya sauces showing mutagenicity after nitrite treatment were 82-678 and 17-2 250 micrograms/mL, respectively. Most soya sauces produced in the USA showed weaker mutagenicity than those produced in Japan and contained lower, if not undetectable, amounts of the three precursors of mutagens. The mutagenicity of MTCA isomers and tyramine accounted for 16-61 and 1-35%, respectively, of the mutagenicity of the soya sauces after nitrite treatment. The mutagen(s) produced from (-)-(1S,3S)-MTCA with nitrite was a minor product(s), the major product being the non-mutagen, (-)-(1S,3S)-1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carbo xylic acid [(-)-(1S,3S)-MNTCA], but the mutagen 4-(2-aminoethyl)-6-diazo-2,4-cyclohexadienone, produced from tyramine with nitrite, was one of the major products.

Carbolines↗
PubMed1984

Kinetics of nitrosation of thioproline, the precursor of a major nitroso compound in human urine, and its role as a nitrite scavenger.

The kinetics of nitrosation of thioproline was studied. The rate of the reaction increased with decrease in pH, and was first-order with respect to nitrite concentration. The reaction rate was proportional to the concentration of total thioproline (free plus protonated), not to that of free thioproline. The initial reaction rate followed the equation: rate = k4 X [thioproline] X [NaNO2] X [H+] The rate constant was found to be 49.4M-2 . sec-1 at pH 2.0 and 37 degrees. Thioproline acted as a nitrite scavenger, and suppressed the formation of a carcinogen, N-nitroso-N-benzylmethylamine, from N-benzylmethylamine and nitrite. More than 90% of the formation of N-nitroso-N-benzylmethylamine was inhibited by adding 20mM thioproline to a reaction mixture containing 20mM N-benzylmethylamine and 20mM sodium nitrite at pH 3.0 and 37 degrees.

Antineoplastic Agents↗
PubMed1984

A new type of N-nitrosamino acid, N-nitroso-L-thioproline and N-nitroso-L-methylthioprolines, found in human urine as major N-nitroso compounds.

In addition to N-nitrosoproline (NPRO), N-nitrosamino acids of a new type containing sulfur were found as major N-nitroso compounds in the urine of seven healthy subjects. These compounds were detected using a gas chromatograph connected with a Thermal Energy Analyzer (GC-TEA), and they were identified as N-nitroso-L-thiazolidine-4-carboxylic acid (N-nitroso-L-thioproline, NTPRO) and the cis and trans isomers of N-nitroso-L-methylthiazolidine-4-carboylic acid (N-nitroso-L-methylthioproline, NMTPRO) by using gas chromatography-mass spectrometry (GC-MS). The amounts of NPRO, NTPRO and NMTPRO found in 100 mL samples of human urine were 65-471 ng, 67-2 250 ng and 275-5 825 ng, respectively. L-Thioproline was nitrosated 20-60 times faster than L-proline by nitrite over the whole range of acidic pH. The precursors of these new-N-nitrosamino acids containing sulfur may be formed by the reaction of L-cysteine with formaldehyde and acetaldehyde in the human body. These sulfur-containing N-nitroso compounds, NTPRO and NMTPRO, in addition to NPRO, could be useful as probes for investigation the dynamics of nitrosation in the human body.

Chromatography, Gas↗
PubMed1983

Bone marrow transplantation for Niemann-Pick mice.

The Niemann-Pick mice which received bone marrow transplants showed a decreased accumulation of sphingomyelin and cholesterol quantitatively in their spleen. The sphingomyelin deposit in the bone marrow was also reduced histochemically. However, the neurological manifestations were not improved by the bone marrow graft.

Animals↗
PubMed1983

Specific quantitation of secretory immunoglobulin A with enzyme immunoassay using activated thiol--Sepharose for separation method.

A specific and sensitive enzyme immunoassay system for human secretory IgA was developed using anti-alpha-chain antibodies coupled to activated thiol-Sepharose, and anti-secretory component antibodies labeled with beta-D-galactosidase from Escherichia coli. The dose response of the enzyme activity in eluate was observed between 3 and 1000 ng of secretory IgA with little cross-reactions with IgA, IgG, IgM and secretory component. The assay method could be employed for the measurement of secretory IgA in saliva, urine, feces, intestine and serum without interferences by the abundant IgA in the same samples.

Animals↗
PubMed1983

Inactivation of potent pyrolysate mutagens by chlorinated tap water.

The potent mutagens 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2, 62450-07-1), 2-amino-6-methyldipyrido-[1,2-a:3', 2'-d]imidazole (Glu-P-1, 67730-11-4) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ, 76180-96-6), isolated from pyrolysates of tryptophan and glutamic acid and from broiled sardines, respectively, were effectively degraded by chlorinated tap water with a concomitant loss of mutagenicity toward Salmonella typhimurium TA98 and TA100. The half-life of 10 microM IQ in the presence of 1.5 ppm of residual chlorine was less than 10 sec; those of Glu-P-1 and Trp-P-2 were 0.5-1 and 2-3 min, respectively. This means that a glass of chlorinated tap water (150 ml) containing 1.5 ppm of residual chlorine can break down about 200 micrograms of these pyrolysate mutagens within a couple of minutes.

Carbolines↗
PubMed1983

Photochemistry of two rhodopsinlike pigments in bacteriorhodopsin-free mutant of Halobacterium halobium.

Two photocycles due to two different pigments were found in membrane vesicles of a bacteriorhodopsin-free mutant of Halobacterium halobium. A pigment absorbing approximately 590 nm halorhodopsin (HR) underwent a faster photocycle with a phototransient at approximately 490 nm (half-time of decay, tau 1/2 = 10 ms). Another third rhodopsinlike pigment (TR) absorbing approximately 580 nm underwent a slower photocycle accompanying a phototransient absorbing below 410 nm (tau 1/2 = 0.8s). The photocycles were measured under various conditions of temperature, NaCl concentration, pH, and in the presence of cholate. All results obtained support the notion that the two photocycles are independent of each other, and the fast or the slow cycle can be abolished after these treatments. At alkaline pH, the wavelength of maximum absorbance of both pigments shifted to blue, but the magnitude of the shift of the pigment undergoing the slow photocycle was much greater than the other. The ratio of the content of the two pigments varies among bacteriorhodopsin-free mutants.

Bacteriorhodopsins↗