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Biomedical subjects

S Kamimura

Publications and source records attributed to S Kamimura.

At least 73 records · Page 4Linked to original sources
PubMed1991

Localization and developmental change of indoleamine 2,3-dioxygenase activity in the human placenta.

Previously, we pointed out the importance of the kynurenine metabolism in fetuses and neonates. We examined localization and developmental change of indoleamine 2,3-dioxygenase activity in human placenta. The indoleamine 2,3-dioxygenase was found localized in syncytiotrophoblast in the placenta. The indoleamine 2,3-dioxygenase activity was not detected in placenta in the early stage of gestation. It was first detected at around 14 weeks of gestation, increased rapidly thereafter and was maintained at high levels till near term. The indoleamine 2,3-dioxygenase activity was significantly lower in placenta with retarded intrauterine development. These results suggest the importance of placental indoleamine 2,3-dioxygenase during fetal development.

Female↗
PubMed1989

High-frequency nanometre-scale vibration in 'quiescent' flagellar axonemes.

The movement of cilia and flagella is based on the interaction between dynein arms and microtubules coupled with ATP hydrolysis. Although it is established that dynein arms cause adjacent microtubules to slide, little is known about the elementary process underlying the force production. To look more closely at the mechano-chemical conversion mechanism, we recently developed an optical method for measuring a nanometre-scale displacement with a time-resolution better than 1 ms. We now report the detection of high frequency (approximately 300 Hz) vibration of sub-nanometre amplitude in non-beating flagellar axonemes. This vibration could reflect the movement of individual activated dynein arms.

Adenosine Triphosphate↗
PubMed1987

[Preoperative radiotherapy of carcinoma of the stomach and breast].

Sixty-one patients with gastric cancer and thirty-seven with breast cancer who had undergone preoperative radiotherapy were analysed retrospectively for assessment of various radiotherapeutic effects and prognosis. Most of the sixty-one patients with gastric cancer were found to be stage III or more with borderline operable lesions on admission. Of the sixty-one patients, sixteen were evaluated postoperatively to be stage I by histopathological examination. The 3-year survival rate in these sixteen patients was an admirable 60%. Of the thirty-seven patients with breast cancer, the 3-year survival rate among twenty-four in Stage III exceeded 90%. This survival rate is very high in comparison with other reports. For radiotherapy we adopted a less-fractionated irradiation method with a large dose instead of the conventional fractionated one. This irradiation method has not only a direct radiotherapeutic effect, but also produces a favorable effect on the host's immunocompetence. For gastric cancer, twice weekly treatment with 5 Gy and 3 Gy per week, and irradiation twice with 20 Gy and 10 Gy for breast cancer were very suitable preoperative irradiation doses.

Breast Neoplasms↗
PubMed1987

[Study of abscopal effect and cellular infiltration of tumor nests using less-fractionated, large-dose radiation].

As reported by several authors, abscopal effect and favorable cellular infiltrations into the tumor nest caused by irradiation suggest the existence of cell immunity in the host. In our present study, as first step to elucidate the mechanism of the fact mentioned above, effects of radiation with a single dose irradiation was estimated in terms of the increase of survival rate and the inhibition of pulmonary metastasis, i.e. abscopal effect in the mice of irradiated tumor burden. Therefore, we examined the resected and pulmonary specimen after irradiation histopathologically. We also examined the effects of the administration of immune modulator PSK and OK-432. Results; 1) Increase of survival rate and inhibition of pulmonary metastasis were observed in groups of mice with inoculated tumor and with again inoculated tumor treated by a single dose irradiation, compared to either the control groups. 2) Also administration of immune potentiator with radiation enhanced the survival rate and inhibition of pulmonary metastasis in all experimental protocols. 3) Remarkable cellular infiltrations of tumor nest after irradiation were observed, and these cellular infiltrations suggest participation of immunoreaction. In the group of using immune modulator, the cellular infiltrations were observed more remarkable than the other groups. 4) Optimal radiation dose was proved to be 30 Gy in this study.

Animals↗
PubMed1986

Turbidimetric studies on microtubule sliding using the stopped-flow-light-scattering method.

The turbidity of axonemes during active sliding of microtubules was analysed using the stopped-flow-light-scattering method with high time resolution. Flagella of sea-urchin spermatozoa were demembranated and used after a brief treatment with trypsin. The turbidity of the suspension of flagellar axonemes during ATP-induced disintegration was measured and its time course fitted to a single exponential function which yielded the rate of disintegration, R(1/sec). R coincided well with the velocity of microtubule sliding, V(microM sec) as determined by cinematomicrographic analysis, i.e., R = 0.22 X V, r = 0.9973. It indicates that turbidimetry is a useful method with which to learn the sliding velocity of microtubules. From the dependency of R on temperature, Q10 of the sliding velocity was estimated to be 2.0-2.3 at 43-820 microM of MgATP.

Adenosine Triphosphate↗
PubMed1985

ATP hydrolysis coupled to microtubule sliding in sea-urchin sperm flagella.

Using sea urchin (Hemicentrotus pulcherimus) sperm flagella, ATP hydrolysis coupled to sliding movement of microtubules was investigated. Flagellar axonemes were pretreated with trypsin and the microtubules induced to slide by addition of ATP (50-1,000 microM) at 0-20 degrees C. Motion-dependent hydrolysis of ATP was observed immediately after the addition of ATP, the rate of which was higher than that of steady state hydrolysis in axonemes without trypsin-treatment, or after complete disintegration. The rate of hydrolysis of ATP divided by the sliding velocity of microtubules reflects the ATP consumption necessary per unit distance of microtubule sliding. This parameter varied according to the experimental conditions in that it increased when the ATP concentration or temperature was decreased. Our results suggest that there is not a strict stoichiometric relationship between ATP hydrolysis and sliding distance in the dynein-tubulin system, indicating that the mechanochemical coupling is different from that in beating axonemes.

Adenosine Triphosphate↗
PubMed1983

[Relationship between radiotherapy and tumor immunity in hosts].

There are several opinions which denied therapeutic effects of preoperative irradiation, however, we have obtained favorable results by preoperative irradiation for the advanced breast and stomach cancers. Because we treated them by less-fractionated irradiation method with a large dose instead of conventional fractionated one. We adopted this kind of radiation method for the purpose of enhancing the antigenicity of the cancer cells (that means to inhibit the suppression of immune reaction in hosts). Cases of advanced breast cancer were irradiated with 30 Gy at once or 10 Gy at three times a week (total 30 Gy) by betatron electron and we treated advanced stomach cancer with twice a week method (5 Gy or 3 Gy each time, total 40 Gy) by 6 MV X-ray. Cellular infiltration into the stroma of malignant tumor is able to be considered as cellular immunity of the tumor. The same reaction could be observed in radiotherapy for cancer by using above method. After preoperative irradiation, we examined the resected specimen histopathologically. Remarkable cellular infiltrations into the tumor nests, such as neutrophils, lymphocytes, macrophages and plasma cells were observed and these cellular infiltrations after the preoperative irradiation were more remarkable than the cases without radiotherapy or with conventional fractionated radiotherapy. The abscopal effects could be seen in several cases. Peripheral lymphocytes, T cells, B cells and blastoid formation rate induced by PHA in vitro were all increased after less-fractionated irradiation. The reaction to 4 kinds of immunological skin tests was also enhanced.

Adult↗
PubMed1983

Dynamic aspects of microtubule sliding in sperm flagella.

The force of microtubule sliding in reactivated sea urchin sperm flagella was determined under defined mechanical conditions by attaching two glass microneedles to a demembranated flagellum and measuring the small displacements of the needle caused by the sliding force. Upon reactivation with a solution containing elastase as well as ATP, oscillatory force generation was observed under an isometric condition, followed by a plateau of isometric force. The average isometric force was about 1 pN per dynein arm which did not change with the ATP concentration (4 to 500 microM).

Adenosine Triphosphate↗
PubMed1982

Microtubule sliding in reactivated flagella.

Recent experimental studies of microtubule sliding in demembranated sea urchin sperm flagella are described. A local iontophoretic application of ATP to a Triton-extracted flagellum elicits a local bending response whose form is in exact conformity with the predictions of the sliding microtubule model. Cinematographic analysis of the microtubule sliding initiated by treating fragments of demembranated flagella with trypsin in the presence of ATP reveals that the speed of sliding is almost constant. This implies that the speed does not depend on the number of dynein arms participating in the generation of sliding force. The distribution of apparent sliding velocities indicates that there is no difference in sliding velocity among the doublets. The sliding velocity depends on MgATP concentration in a manner consistent with Michaelis-Menten kinetics. The sliding velocity of doublets in trypsin-treated axonemes is close to the maximum velocity of relative sliding taking place between adjacent doublets in beating flagella reactivated at the same MgATP concentration.

Adenosine Triphosphate↗
PubMed1980

Enzymatic conversion of cephamycin C by D-amino acid oxidase from Trigonopsis variabilis.

D-Amino acid oxidase (EC 1.4.3.3) systems from Trigonopsis variabilis SANK 59963 were found to catalyze cephamycin C. The reaction products were assigned to 7 beta-(5-carboxy-5-oxovalerylamido)-7 alpha-methoxy-3-carbamoyl-3-cephem-4-carboxylic acid, and 7 beta-(4-carboxy-butyrylamido)-7 alpha-methoxy-3-carbamoyl-3-cephem-4-carboxylic acid, respectively. D-Amino acid oxidase from hog kidney was not able to catalyze cephamycin C.

Amino Acid Oxidoreductases↗
PubMed1979

Stereo-specific synthesis of 3-trifluoromethylcephalosporin derivative by microbial acylase.

Cephalosporin acylase (EC 3.5.1.11) obtained from Kluyvera citrophila ATCC 21285 was found to catalyze synthesis of 7-[2-(2-thienyl)acetamido]-3-trifluoromethyl-3-cephem-4-carboxylic acid from methyl thienylacetate and dl-7-amino-3-trifluoromethyl-3-cephem-4-carboxylic acid. The enzymatically-synthesized compound showed [alpha]25 D + 42.7 degrees (c 0.058, MeOH) and its biological activity was about twice as much as that of racemic 7-[2-(2-thienyl)acetamidol]-3-trifluoromethyl-3-cephem-4-carboxylic acid chemicall synthesized. As a result, N-acylation by this enzyme was demonstrated to be asymmetric synthesis.

Amidohydrolases↗