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Biomedical subjects

S Muramatsu

Publications and source records attributed to S Muramatsu.

At least 163 records · Page 9Linked to original sources
PubMed1987

Role of macrophages as modulators but not as autonomous accessory cells in the proliferative response of immune T cells to soluble antigen.

The role of murine macrophages (M phi) and that of splenic dendritic cells (DC) were investigated in the antigen-specific proliferative response of memory T cells of mice primed with key-hole limpet hemocyanin (KLH) 6 weeks or more before. Peritoneal M phi, whether expressing Ia antigens or not, did not function as autonomous accessory cells (A cells). A-cell activity of the spleen adherent cell population, which comprised M phi in the majority and DC in the minority, was abolished by eliminating DC with a DC-specific monoclonal antibody and complement, and regained by the addition of a small number of DC. Though M phi did not function as autonomous A cells, they augmented the proliferative response in the presence of a small number of DC. This occurred not only in the presence of free antigen, but also when DC and/or M phi were pulsed with antigen. A culture supernatant of M phi having interleukin-1 activity was effective in enhancing the proliferation of T cells which responded to antigen-pulsed DC. On the other hand, interleukin-2 did not replace DC even in the presence of antigen-pulsed Ia+ M phi. We also investigated recently primed T cells, but no evidence was obtained in favor of the competence of M phi as autonomous A cells.

Animals↗
PubMed1987

Development of a selective clean-up method using immobilized antibody and its application to HPLC and GC/MS determination of a carbacyclin derivative, CS-570, in plasma.

Methods for the determination of CS-570, a chemically stable prostacyclin analogue, in plasma were developed by using an immobilized antibody column followed by fluorescence HPLC and GC/MS. The CS-570 antibody, obtained from rabbit plasma by giving CS-570-BSA for a few months, was coupled to Sepharose 4B and used as extraction phase for sample clean-up and extraction of the drug. A plasma sample was applied to this column, washed with water and the drug was eluted with 90% acetonitrile. 0.02% (w/v) 9-anthryldiazomethane (ADAM) was added to the extract to form a fluorescent derivative. The CS-570-ADAM adduct exhibited high sensitivity when applied to HPLC with fluorescence detection and column switching. The detection limit was 1 ng/mL when 1 mL of plasma was available. Additionally, a pentafluorobenzyltrimethylsilyl derivative of CS-570 showed excellent sensitivity when determined by capillary GC interfaced to negative ion chemical ionization MS using a stable isotope labelled analogue as an internal standard.

Animals↗
PubMed1987

Developmental fall in whole body protein turnover of chick embryos during incubation.

Whole body protein turnover was measured in chick embryos during incubation to investigate whether or not there is a fall in fractional rates of protein synthesis and degradation during development. Stable isotopically labelled [15N]phenylalanine was injected intraperitoneally into embryos on days 12 and 19. From 60 to 90 min after injection the isotope enrichment in free and protein-bound phenylalanine was measured with a selected-ion gas-chromatograph mass-spectrometer. The results showed that from days 12 to 19 of incubation, there was a remarkable reduction in fractional rates of protein synthesis and degradation in the whole body of chick embryos. During embryonic growth, protein synthesis per unit of RNA that is, the minimum amino acid translation rate of RNA, did not change significantly, whereas the RNA:protein ratio was reduced to one-third from days 12 to 19 of incubation. It was concluded, therefore, that the dramatic fall in fractional synthesis rate in chick embryos would be entirely attributable to the rapid increase in protein content, thereby changing the RNA:protein ratio in parallel with the fractional synthesis rate.

Animals↗
PubMed1987

Activity of motor units during concentric and eccentric contractions.

Motor unit activity was investigated in the biceps brachii of twelve men during concentric (CC) and eccentric (EC) contractions by means of computer aided intramuscular spike amplitude-frequency (ISAF) histograms and surface EMG frequency power spectral analyses. Simultaneous recordings of the intramuscular and surface EMG signals were made during both types of contractions with the elbow joint angle varying from 30 to 150 degrees in reference to a fully extended position. Results demonstrated that r.m.s. amplitude and mean power frequency of the surface EMG were significantly higher during CC, particularly at shorter muscle length; e.g., 259 vs. 131 microV (p less than 0.01) and 102 vs. 91 Hz (p less than 0.05). The intramuscular spike recordings made at 45, 90 and 135 degrees showed greater motor unit (MU) activities during CC along with the presence of MUs with relatively large spike amplitude. The pooled data on the ISAF histograms revealed significantly greater mean MU spike amplitude and frequency during CC as compared to EC; e.g., 439 vs. 108 microV and 16.1 vs. 13.0 Hz at 135 degrees, respectively. These data suggest that EC is associated with much less pronounced MU recruitment and rate modulation due to economical tension development which might be a result of better utilization of elastic energy, particularly those inherent in the actin-myosin cross bridges and also a favorable length-tension relationship under the present experimental conditions.

Electromyography↗
PubMed1987

Accessory cell functions of dendritic cells and macrophages in the thymic T-cell response to Con A.

Accessory cell (A cell) functions of splenic dendritic cells (DC) and peritoneal macrophages (M phi) were investigated in the Con A-stimulated proliferative response of thymic T cells. DC were more efficient as A cells than M phi in respect of their necessary cell numbers, Con A dose and culture period required for optimal response. Con A-pulsed T cells proliferated with the aid of lymphocyte activating factor(s) (LAF) derived from M phi, even in the apparent absence of A cells. Con A-pulsed M phi were superior to unpulsed M phi in the secretion of LAF to induce a high response of Con A-pulsed T cells. A cell activity of M phi in different preparations appeared to parallel the ability to secrete LAF, and was totally abolished by fixation of M phi with paraformaldehyde. The fixation of DC, however, resulted in only a partial reduction of the A cell activity. These results argue that both DC and M phi can serve as A cells in the T-cell response to Con A, but that the mechanism to manifest A cell activity is somewhat different between DC and M phi.

Animals↗