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Biomedical subjects

A Sakai

Publications and source records attributed to A Sakai.

At least 469 records · Page 26Linked to original sources
PubMed1979

Stimulation of allogeneic lymphocytes by skin epidermal cells in the rat.

The ability of skin epidermal cells to induce allogeneic lymphocytes into proliferation was examined in mixed skin cell-lymphocyte culture reaction (MSLR). The stimulating capacity of skin cells was reduced significantly by trypsin digestion, although the damage was repaired by incubation at 37 C for 3 hr. The optimal concentration of mitomycin C for treatment of stimulating cells in the MSLR differed from that in mixed lymphocyte culture reaction (MLR). Irradiation rendered them three to four times more stimulatory than did mitomycin C. Removal of adherent cells from responding cells by passage through a nylon-wool column gave a substantial elevation of the MSLR. The lymphocytes cocultured with skin cells in the primary MSLR incorporated 3H-thymidine, with the peak at the 6th day of culture. If the lymphocytes primed in the MSLR were restimulated with skin cells from the same stimulating strain, the primed lymphocytes responded promptly and in great magnitude.

Animals↗
PubMed1979

Minimum length of time required for alloantigen recognition.

The minimum length of time required for lymph node lymphocytes to recognize alloantigens in vitro was examined in mixed skin cell-lymphocyte culture reactions. Responding lymphocytes in the mixture were successfully separated from stimulating skin cells by Ficoll-Hypaque gradient sedimentation. Lymphocyte activation by allogeneic skin cells took place within 15 min of contact. The amount of measured stimulation was approximately 30% of that produced by an equal concentration of antigen present continuously in culture. The presence of alloantigen was no longer needed after 24 hr. Several control experiments were made in order to exclude the effects of contamination and culture conditions. Identical results were obtained with allogeneic hepatocytes. These data indicate that the recognition of alloantigen leading to lymphocyte proliferation may occur during the early period of contact.

Animals↗
PubMed1979

[Effect of oligopeptides containing L-Phe, L-Tyr, L-Trp, L-His or L-Met on the excitability of the 2 giant neurons of the African giant snail (Achatina fulica Ferussac)].

Effects of about ninety oligopeptides, containing L-Phe, L-Tyr, L-Trp, L-His and L-Met, on the excitability of two identifiable giant neurones (the PON, periodically oscillating neurone ; and the TAN, tonically autoactive neurone) of Achatine fulica Férussac were examined. Three oligopeptides, L-Lys-L-Phe-L-Tyr, L-Phe-L-Tyr and L-Phe-L-Trp, showed an inhibitory effect on the PON. However, this effect on the PON was weaker than that of the same three peptides on the TAN. [The latter has been reported in previous papers (1 to 3)]. Besides the three oligopeptides mentioned, four peptides, L-Phe-L-Phe, L-Phe-L-Phe-L-Phe, L-Tyr-L-Tyr and L-Tyr-L-Tyr-LTyr, still showed a weak inhibitory effect on the TAN in a high concentration.

Action Potentials↗
PubMed1979

Inhibitory effects of aromatic oligopeptides on the excitability of identifiable giant neurones of an African giant snail (Achatina fulica Férussac).

Effects of an aromatic tripeptide, L-Lys-L-Phe-L-Tyr and its related dipeptides on the excitability of two identifiable giant neurones (the TAN, tonically autoactive neurone and the PON, periodically oscillating neurone) in the suboesophageal ganglia of the African giant snail, Achatina fulica Férussac, were examined. Of 33 substances examined, three aromatic oligopeptides showed a marked inhibitory effect on the TAN excitability. The critical concentrations of these substances in bath application were: L-Lys-LPhe-L-Tyr (6.6 x 10(-6) approximately 2.2 x 10(-5) M), L-Phe-L-Tyr (9.1 x 10(-6) approximately 3.0 x 10(-5) M) and L-Phe-L-Trp (2.4 x 10(-5) approximately 7.3 x 10(-5) M). The microdrop application (100 micron in diameter) of a solution of the three inhibitory oligopeptides on the TAN surface hyperpolarized the TAN membrane potential and eliminated the spike discharges, in both the physiological and the chloride-free (replaced with acetate) conditions. The current-voltage relationships (I-V curve) of the TAN neuromembrane were measured by the injection of a transmembrane triangular current. The TAN I-V curve measured in the presence of L-Lys-L-Phe-L-Tyr or L-Phe-L-Trp was almost concordant to that of the normal state, if the two I-V curves were superimposed using the firing level as the reference point. The same three aromatic oligopeptides also showed an inhibitory effect on the PON excitability. The critical concentrations needed to produce the effects were much higher than those in the case of the TAN.

Animals↗
PubMed1979

Excitatory effects of ergot alkaloids and their derivatives on the excitability of an identifiable giant neuron of the African giant snail (Achatina fulica Férussac).

The effects of various ergot alkalids and related substances on the neuronal excitability were examined using a spontaneously firing neuron (PON, periodically oscillating neuron) identified in the suboesophageal ganglia of the African giant snail (Achatina fulica Férussac). Of the substances examined, ergometrine and methylergometrine had a marked excitatory effect on the neuron (their critical concentration by bath application: 5 x 10(-6) kg/l). D-lysergic acid (the critical concentration: 3 x 10(-5) kg/l), D-lysergic acid amide (3 x 10(-5), D-lysergic acid 3-hydroxypiperidinamide (3 x 10(-5) and D-lysergic acid 4-hydroxypiperidinamide (10(-4) had also an excitatory effect which was weaker than that of the two alkaloids mentioned above. Agroclavine and elymoclavine had a very slight excitatory effect in some cases. The other substances examined, for example, lysergine, 9, 10-dihydro-D-lysergic acid, 9, 10-dihydro-D-lysergic acid amide, nicergoline, metergoline, methysergide, ergotamine, bromocriptine, lergotrile etc., had no effect on the neuron at a high concentration (10(-4) kg/l). When local (microdrop) application of ergometrine and methylergometrine in the physiological state was performed, the depolarizing shift of the PON membrane and exaggeration of the membrane potential oscillations were observed. In the Na+-free (replaced with Li+) state, local application of the two effective alkaloids produced a marked frequency increase of tonic spike discharges with depolarization of the neuronal membrane.

Animals↗
PubMed1978

Liver and immune responses. IV. Characteristics of the liver cell-lymphocyte interaction.

Rat liver cells prepared by collagenase treatment and separated by density gradient centrifugation with Ficoll-Hypaque solution (specific gravity 1.120), containing only hepatocytes (80%) and Kupffer cells (20%), were found to stimulate strongly Ag-B-incompatible lumphocytes without 2-mercaptoethanol in culture. The same liver cells could also stimulate Ag-B-compatible lymphocytes in the presence of 2-mercaptoethanol. A positive response was only seen when the liver cell numbers were 1 approximately 2% of the responding lymphocytes. Viable liver cells inhibited the reaction in a two-way culture.

Animals↗