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Biomedical subjects

M Kojima

Publications and source records attributed to M Kojima.

At least 883 records · Page 49Linked to original sources
PubMed1981

Effects of disopyramide on transmembrane action potentials in guinea-pig papillary muscles.

The effects of disopyramide on the transmembrane action potential in guinea-pig papillary muscles were studied with special reference to the dependence of the effects on the external concentrations of K+ ([K+]0), stimulation rates, and diastolic intervals. Disopyramide, 2 micrometer, prolonged the 90% action potential duration (ADP90) without changing the maximum rate of phase 0 depolarization (Vmax) (class 3 action), whereas disopyramide, 20 micrometer, reduced Vmax, (class 1 action). The class 3 action was prominent in 2.7 and 5.4 mM [K+]0, at 0.25--1 Hz, and so was the class 1 action in 8.1 mM [K+]0, at 2--5 Hz. Disopyramide, 20 micrometer, enhanced the rate-dependent reduction in Vmax only in 8.1 mM [K+]0. Neither concentration of disopyramide altered the recovery kinetics of APD90 in the premature responses in three [K+]0, but slowed that of Vmax only in 8.1 mM [K+]0. These results indicate that the manifestation of class 3 action of disopyramide is favored with low concentrations of the drug, low [K+]0, and low stimulation rates, whereas the reverse is true in the class of the class 1 action.

Action Potentials↗
PubMed1981

An electron microscopic study on the reticuloendothelial cells in the lymph nodes.

In an attempt to clarify the cytological characteristics of the RES cells in the lymph nodes and their embryological correlations, lymph nodes and lymph node anlages of germ-free rats, nude mice, and human fetuses were light and electron microscopically examined. On the basis of differences of intracellular organelles, their behaviors for reticulum fibers and of endogeneous peroxidatic activity, histiocytes should be reasonably distinguished from the cells conventionally called reticulum cells. Reticulum cells and histiocytes respectively are destined to differentiate in different directions from the early stage of development of the lymph node anlage. Sinus endothelial cells are ontogenetically originated and differentiated from the endothelial lining cells of lymphatic vessels. Primitive reticular cells are differentiated into mature reticulum cells in the lymph nodes, they transform into the lympho-reticular cells, further into lymphoblasts, and finally develop into medium-sized lymphocytes.

Animals↗
PubMed1981

An ultrastructural study of the primary follicle in the lymph node.

The present authors have studied the cellular composition of the primary follicle (PF) in the germ-free rat lymph nodes and the development of PF in the human lymph node anlages by using the light- and the electron microscopy. According to the ultrastructural study, the cellular composition of PF in the germ-free rat lymph nodes and classified into five cell types, 1) lymphocytic cells (small and medium-sized lymphocytes), 2) large lymphocytes (= large germinal center cells), 3) reticulum cells with desmosomes (RED), 4) desmodendric cells (DDC), and 5) histiocytes. The interstitial cells with desmosome are classified into DDC and RED based on the relationship to collagenous fibers and the morphological differences. There are amorphous electron-dense intercellular materials among the cytoplasmic processes of DDC, which are distinguished from histiocytes based on the morphological differences. PF emerges as a spherical aggregation of young DDC straight underneath the marginal sinus in the outer cortex of the human embryonal lymph node anlages on the 16th fetal week.

Animals↗
PubMed1981

[Effects of afloqualone, a centrally acting muscle relaxant, on the sleep-wakefulness cycle in cats with chronically implanted electrodes (author's transl)].

The present study was carried out to elucidate whether or whether not afloqualone has a hypnotic action because of its similarity in chemical structure to methaqualone. In the sleep-wakefulness cycles during the 8-hour observation period (9:00-17:00), afloqualone increased the percentages of resting (REST) and slow wave light sleep (SWLS) stages at a dose of 25 mg/kg (p.o.), producing a moderate muscle relaxation. Even at a dose of 50 mg/kg (p.o.) where a marked muscle relaxation was produced, afloqualone had no influence on the percentage of slow wave deep sleep (SWDS) stage, though it increased the percentages of SWLS and decreased the percentages of awake (AWK), REST and fast wave sleep (FWS) stages. On the other hand, tolperisone . HCl, chlormezanone, methaqualone and pentobarbital . Na, used as the reference drugs, all increased the percentage of SWDS stage, but either decreased or had no effect on the percentages of the other four stages at pharmacologically effective doses. From these results it was concluded that afloqualone seems to be devoid of a hypnotic action and has different effects on the sleep-wakefulness cycle than those of both the hypnotics and the other muscle relaxants used.

Animals↗
PubMed1981

Mouse alloantibodies capable of blocking cytotoxic T cell function. III. Studies of the mechanism of blocking of CML by anti-Lyt-2 antibodies.

Attempts were made to analyze the mechanism of action of anti-Lyt-2 antibody in blocking of CML in the absence of complement. Preincubation of killer cells with anti-Lyt-2 antibody followed by washing was found to abrogate the inhibitory effect of the antibody on target cell lysis, whereas an equivalent amount of the antibody present throughout the culture period caused marked inhibition. The failure of pretreatment with anti-Lyt-2 antibody to cause inhibition of CML might be due to rapid turnover of Lyt-2 molecules. Delayed addition of the anti-Lyt-2 antibody to CML cultures decreased the inhibition observed, which indicated that the antibody must be present during early stages of killing in order to exert significant inhibitory effects. The partitioning of CML according to requirements for divalent cations showed that anti-Lyt-2 antibody acts on killer cells during the Mg++-dependent stage of killing. In addition, the antibody was shown to be capable of reversing certain events occurring during this stage. These data are consistent with a role for Lyt-2 molecules during the antigen recognition stage of cell-mediated lysis. However, the exact function of the Lyt-2 molecule remains unknown.

Animals↗
PubMed1980

Effects of tocainide and lidocaine on the transmembrane action potentials as related to external potassium and calcium concentrations in guinea-pig papillary muscles.

Effects of lidocaine and tocainide on transmembrane potentials were studied in isolated guinea-pig papillary muscles, superfused with modified Tyrode's solution containing either 5.4, 2.7, 10.0 or 8.1 mmol/l potassium concentration, [K]0. The last solution applied contained either 1.8 (normal [Ca]0) or 7.2 mmol/l [Ca]0 (high [Ca]0. The concentrations of lidocaine and tocainide used were 18.5, 36.9 and 73.9 mumol/l and 43.7, 87.5 and 174.9 mumol/l in 5.4 mmol/l [K]0 solution and 36.9 and 87.5 mumol/l in the other solutions, respectively. At the driving rate of 1 Hz in 5.4 mmol/l "K]0 solution, both drugs produced dose-dependently a reduction of maximum rate of rise of action potential (Vmax), together with a prolongation of the relative refractory period. Vmax decreased progressively as the driving rate was increased from 1 Hz (for lidocaine) and from 0.25 Hz (for tocainide) to 5 Hz. This action was accentuated dose-dependently. A slow component (time constant tau = 232 ms for lidocaine, 281--303 ms for tocainide) and slower component (tau = 2.1--3.8 s for tocainide) of the recovery (reactivation) of Vmax were observed in premature responses at 0.25 Hz and in the first response after interruption of the basic driving rate at 1 Hz. All these effects were accentuated with rising [K]0 and attenuated in the high [Ca]0 solution. Both drugs abbreviated the action potential duration at 50% (APD50) and 90% (APD90) levels at 5.4, 8.1 and 10.0 mmol/l [K]0 but not at 2.7 mmol/l [K]0 nor a high [Ca]0 at 1 Hz. These [K]0-dependent effects of lidocaine on Vmax were successfully simulated by the model proposed by Hondeghem and Katzung (1977), with a slight change in parameter values. The mode of interaction of lidocaine with sodium channels in the open, closed and rested states was deduced from these results.

Action Potentials↗