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Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 253 records · Page 14Linked to original sources
PubMed1979

Proton transfer kinetics in the lowest excited state of 1,N6-ethenoadenosine as revealed by fluorescence lifetime measurements.

Fluorescence lifetimes have been examined of 1, N6-ethenoadenosine (epsilon Ado), 1-methyl-ethenoadenosine (m1 epsilon Ado+), 9-methyl-ethenoadenosine (m9 epsilon Ado+), N1-deazaethenoadenosine (N1-deaza-epsilon Ado, and 9-methyl-N1-deazaethenoadenosine (m9N1-deaza epsilon Ado) at various pH's in the 7.5 approximately 1.5 region and at 20 degrees C. From an analysis we have reached the following conclusions. (1) The observed fluorescence of epsilon Ado is caused by the unprotonated, neutral, excited species epsilon Ado not not only at pH 7 but also at pH 2. (2) pKa of the excited epsilon Ado is lower than that of the ground state epsilon Ado. (3) The rate constant of protonation in the excited state is about 10(10) sec-1 M-1.

Adenosine↗
PubMed1978

Bioassay of cholecystokinin in the duodenal mucosa.

Cholecystokinin (CCK)-like activities in the duodenal mucosa were measured by bioassay in patients with duodenal ulcer, cholelithiasis and some other gastrointestinal diseases as well as in healthy normal subjects. The mean CCK-like activity of the duodenal mucosa in patients with duodenal ulcer and cholelithiasis was 0.405 Ivy dog units per milligram and 0.376 Ivy dog units per milligram of dry weight of the duodenal mucosa (IDU/mg d.w.), respectively. Both these figures are significantly higher than 0.180 IDU/mg d.w. in normal subjects (p less than 0.005, p less than 0.005, respectively). It can be speculated that the CCK-level of the duodenal mucosa in patients with cholelithiasis may be regulated by a feedback mechanism and CCK in patients with duodenal ulcer may act physiologically for the cure of duodenal ulcer.

Adolescent↗
PubMed1978

Exposure of DNA bases induced by the interaction of DNA and calf thymus DNA helix-destabilizing protein.

The reaction of chloroacetaldehyde with adenine bases in DNA to give a fluorescent product was used to study the availability to intermolecular reaction of positions 1 and 6 of adenine in DNA complexes with calf thymus DNA helix-destabilizing protein. No inhibition of this reaction was observed when heat-denatured DNA was complexed with the protein at a protein/DNA weight ratio of 10:1, compared to free DNA. On the contrary, the same reaction was inhibited markedly for denatured DNA in the presence of calf thymus histone HI at protein/DNA weight ratio of 2:1. Furthermore, the exchange rate for hydrogens of amino and imide groups of DNA bases in DNA strands with deuterium in the solvent was totally unaffected upon complexing of DNA with the DNA helix-destabilizing protein as examined by stopped-flow ultraviolet spectroscopy. These results indicate that the DNA helix-destabilizing protein forms a complex with single-stranded DNA, leaving DNA bases uncovered by the protein. The fluorescence intensity of DNA pretreated with chloroacetaldehyde was amplified by nearly 3-fold upon addition of the DNA helix-destabilizing protein. The possibility of "unstacking" of DNA bases induced by the protein is discussed.

Acetaldehyde↗
PubMed1978

Crystallization of arginine-, formylmethionine-tyrosine-, and glycine-transfer RNAs from Escherichia coli.

Crystals as large as 0.5 X 0.3 X 0.2 mm of purified arginine-transfer RNA from Escherichia coli have been prepared by a vapour diffusion method. X-ray diffraction photographs showed that the crystals gave reflections up to 3.7 A spacing. They have a trigonal space group P31 2 1 (OR P32 2 1) and cell-dimensions a=97.2, b=97.2, c=94.8A. Crystals of a mercury derivative of this transfer RNA have also been obtained, and an X-ray diffusion photography of one of them is presented. Formylmethionine-transfer RNA from E. coli was crystallized in various forms, and the appearance of the polymorphs was found to depend upon the amount of spermine in the solution from which the crystallization took place. Crystals of tyrosine-transfer RNA and glycine-transfer RNA have also been obtained.

Arginine↗
PubMed1978

[Effects of various drugs on the lipolytic actions caused by catecholamines and methylxanthine derivatives in white adipose tissues. 1. Effects of procaine and xylocaine (author's transl)].

Effects of procaine and xylocaine on the lipolytic actions caused by catecholamines and methylxanthine derivatives in white adipose tissues from rats were investigated. Both procaine and xylocaine remarkably inhibited the lipolyses caused by norepinephrine, epinephrine, caffeine and theophylline. Xylocaine inhibited the lipolysis more strongly than procaine, and also inhibited the basal lipolysis. The inhibition by either procaine or xylocaine appeared 60 minutes after the addition of the norepinephrine-induced lipolytic action. The antilipolytic action of procaine was evident in medium containing 2 mM EDTA instead of Ca2+, and its antilipolytic action was accelerated by increasing Ca2+ concentration in the medium. From these positive results, we suggest that both procaine and xylocaine have an antilipolytic effect, and this effect is closely dependent on the Ca2+ concentration in the medium.

Adipose Tissue↗
PubMed1978

[Studies on the excitation-metabolism coupling mechanism in brown adipose tissues, 2; Effects of K+ and norepinephrine on the lipolysis in brown adipose tissues (author's transl)].

This investigation was undertaken to clarify the lipolytic response caused by K+ and norepinephrine in brown adipose tissues. 1. Lipolytic response was obviously observed at the concentration of 50 mM in the K+-induced stimulation, and at 1.0 microgram/ml in the norepinephrine-induced stimulation, respectively. 2. K+- and norepinephrine-stimulated lipolysis were inhibited in the Ca2+-deficient tissues, and were inhibited by the addition of Mg2+, Mn2+ and La3+. 3. In the K+-stimulated lipolysis Ca2+ could be substituted only by Sr2+, while in the norepinephrine-stimulated lipolysis the substitution was possible with both Sr2+ and Ba2+. 4. K+- and norepinephrine-stimulated lipolysis were inhibited by the addition of propranolol and procaine. Accordingly, these positive results suggest that K+- and norepinephrine-stimulated lipolysis are dependent on the presence of Ca2+, and are related to the movements of Ca2+ and cyclic AMP system in the cells.

Adipose Tissue, Brown↗