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Biomedical subjects

Y Hara

Publications and source records attributed to Y Hara.

At least 775 records · Page 43Linked to original sources
PubMed1980

Protoplast Fusion: EFFECT OF LOW TEMPERATURE ON THE MEMBRANE FLUIDITY OF CULTURED CELLS.

The relation between the composition of the phospholipid molecular species in a cell membrane and the velocity of protoplast fusion was studied using cells cultured at a low temperature (10 C). Cells cultured at a low temperature contained larger proportions of phospholipids of low phase transition point, the 1,2-dilinoleoyl-type, than those cultured at a normal temperature (25 C). When treated with polyethylene glycol 6000, protoplasts from cells cultured at 10 C fused and progressed to the fused sphere stage more rapidly than did those from cells cultured at 25 C.

Journal Article↗
PubMed1980

Actions of 4-aminopyridine on vascular smooth muscle tissues of the guinea-pig.

1 Effects of 4-aminopyridine (4-AP) and procaine on the membrane and contractile properties of smooth muscle cells of the guinea-pig pulmonary artery and portal vein were observed.2 The membrane potential and length constant of smooth muscle cells of the guinea-pig pulmonary artery were -53.2 mV and 1.2 mm, respectively, and those of the portal vein were -52.6 mV and 0.71 mm, respectively. The membrane was electrically quiescent in the pulmonary artery and it was electrically active in the portal vein.3 Both 4-AP and procaine depolarized the membrane, increased the membrane resistance and suppressed the rectifying properties in both tissues. Both agents evoked a graded response from the muscle membranes of the pulmonary artery by outward current pulse. Procaine had a greater effect than 4-AP on the above membrane properties.4 4-AP (10(-5) M) produced contraction without depolarization of the membrane. The contraction evoked by 10(-5) M 4-AP was completely suppressed but that evoked by 5 x 10(-4) M 4-AP was only partly suppressed by phentolamine (10(-7) M). However, the contraction evoked by procaine was not suppressed by phentolamine.5 4-AP enhanced but procaine suppressed the amplitude of 118 mM [K](0)-induced contraction.6 The results suggest that 4-AP and procaine suppress K-conductance of the muscle membrane, and 4-AP but not procaine increases noradrenaline release from the nerve terminal. Presumably intracellular free Ca concentrations are also modified by these agents. The effects of 4-AP and procaine on the vascular muscle were compared with those on other excitable tissues.

4-Aminopyridine↗
PubMed1980

Platelets as a source of growth-promoting factor(s) for tumor cells.

Human platelet lysate was shown to contain growth-promoting activity for four well-established malignant cell lines. Platelet lysate was able to support their cell proliferation without plasma or serum, indicating that platelets contained "survival factor" as well as mitogenic factor for these tumor cells. The growth-promoting activity was nondialyzable, heat stable up to 56 degrees, and partially trypsin labile, but it was completely destroyed by periodate oxidation, suggesting that a glycoprotein or glycopeptide may be the active principle. The activity was released from platelets aggregated by thrombin or collagen but not by adenosine diphosphate. This suggests that alpha-granules may be the principle storage site for growth-promoting activity.

Animals↗
PubMed1980

Characterization of the platelet-aggregating activity of tumor cells.

Two lines of mouse tumor cells were shown to be capable of aggregating mouse and rabbit platelets in vitro. This process required higher Mg2+ concentrations than were needed by other commonly used platelet-aggregating agents. Platelet-aggregating activity was also found in tumor cell membrane fragments. This membrane-bound platelet-aggregating material contained protein, lipid, and carbohydrate moieties. The presence of all three appeared to be essential for stimulating platelet aggregation. Destruction of any component abolished its activity: protein by trypsin; lipid by phospholipase A2 and non-ionic detergents; and sialic acid by neuraminidase. Platelet aggregation induced by tumor cell membrane fragments was associated with a secretory release reaction. In this process, growth-promoting activity for tumor cells was also released from platelets. These results underline the importance of platelets in establishing tumor metastases.

Adenocarcinoma↗
PubMed1979

The electrical activity recorded from smooth muscle of the circular layer of the human stomach.

The membrane properties of circular muscles of 55 human stomachs were investigated by microelectrode and double sucrose gap methods. The membrane potential of the circular muscle of the corpus region was -57 mV and no regional difference was evident as compared with tissues from the antrum and cardia. The stomach muscle presented cable like properties, and the length constant measured in the corpus region was 1.34 mm. The circular muscle of all regions of the stomach exhibited slow waves. The amplitude and duration of slow waves varied markedly (the mean values were 18 mV and 6 s, respectively). The Q10 value for the slow wave was 2.4. The slow wave could be divided into two different components (first and second component) by application of electrical current or by using solutions with various ionic environments. Na ions had more effect on the spike component and Ca ions on the second component. The generation of the first component of the slow wave was blocked by either Na-free, K-free, Ca-free, or Cl-deficient solution but this component reappeared by application of outward current pulse, except in Cl-deficient solution. These results suggest that the generation of slow wave depends on more than one type of ion and that metabolic factors do indeed play a role. Membrane properties of the human stomach were compared with those of the guinea-pig stomach.

Action Potentials↗