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M Kasai

Publications and source records attributed to M Kasai.

At least 181 records · Page 10Linked to original sources
PubMed1996

Two modes of activity-dependent synaptogenesis of cerebral neurons in vitro.

Effects of transduction activity and transmission activity on synaptogenesis of chick cerebral neurones in dissociated cell culture were studied electrophysiologically using two blockers for these activities, tetrodotoxin (TTX) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), respectively. CNQX inhibited the increase of evoked EPSCs more effectively than TTX, whereas both blockers similarly reduced the increase of miniature EPSCs (Minis). These data indicated that not only transduction-dependent transmission activity but also transduction-independent spontaneous activity regulate the synaptic efficiency. These two activities are suggested to change the quantal amplitude and the number of synaptic sites, respectively.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1996

Okadaic acid gives concentration-dependent reciprocal effects on the fluid phase endocytosis activated by Ca2+ and phorbol 12-myristate 13-acetate.

Incubation of a human fibrosarcoma cell line HT-1080 in increasing concentration of Ca2+ was found to enhance endocytic internalization of a fluid phase marker, horseradish peroxidase. At 16.8 mM Ca2+, generation of the effect required incubation for more than 45 min. The effect was reversed by removal of the excess ion for 30 min. Monitoring the intracellular concentration showed that the incubation induced a transient large Ca2+ influx followed by a recovery to 230 +/- 50 nM instead of the normal level of 83 +/- 5 nM. The activation was not inhibited by inhibitors of protein kinases nor a cAMP antagonist. In contrast, the effect was prevented by okadaic acid (OKA) at 100 nM without detectable effect on the basal activity. Fluid phase uptake by HT-1080 cells was also enhanced by phorbol 12-myristate 13-acetate (PMA). In contrast to the case with Ca2+, OKA at 100 nM did not prevent the PMA effect but further enhanced the endocytosis. The effect of OKA was concentration-dependent, as the reagent at 1 microM inhibited not only both the activation but also the basal activity. In Ca(2+)- or PMA-stimulated cells, FITC-dextran was delivered to endosomes that had been labeled with TRITC-transferrin. In contrast, following treatment with a combination of PMA and 100 mM OKA, fluid phase was internalized in vesicular compartments devoid of transferrin labeling. These results suggest that, through differential modifications of protein phosphorylation, endocytosis can be enhanced distinctively either by employing conventional receptor-bearing compartments or generating a new endosomal population.

Biological Transport↗
PubMed1996

Difference in antigen presentation pathways between cortical and medullary thymic epithelial cells.

Antigen presentation by thymic epithelial cells (TEC) to T cells that undergo maturation is one of the major events in the selection of the T cell repertoire. We have already reported that medullary TEC lines (mTEC) established from newborn C57BL/6 (H-2b) mice are able to present a soluble antigen, ovalbumin (OVA), to OVA-specific, I-Ab restricted helper T cell lines but cortical TEC (cTEC) lines are not (Mizuochi, T. et al., J. Exp. Med. 1992. 175: 1601). In this report, to clarify the cause of this difference, we analyzed the biochemical nature as well as the distribution of both major histocompatibility complex (MHC) class II molecules and invariant chains (Ii) in both TEC by immunoprecipitation and laser confocal scanning microscopic analysis, as well as the expression of mRNA encoding H-2Ma or H-2Mb. Our results demonstrate that cTEC and mTEC are both able to present peptide antigens to peptide-specific, I-Ab-restricted helper T cell hybridoma and are able to present class II MHC alloantigens to an I-Ab-specific T cell line, that mRNA for H-2Ma and H-2Mb are expressed in both TEC, that cTEC and mTEC apparently incorporate tetramethylrhodamine isothiocyanate-labeled OVA in the same manner, and that the SDS-stable MHC class II molecules, onto which peptides were loaded, are formed in both cTEC and mTEC. However, these molecules were more rapidly degraded in mTEC than in cTEC. In addition, two Ii-derived polypeptides of approximately 21 kDa and 10 kDa were precipitated by the anti-class II monoclonal antibody Y3P; 10-kDa polypeptides were detected in the both TEC, while 21-kDa polypeptides were detected only in cTEC. Finally, beta chains of MHC class II with less sialylated oligosaccharides were precipitated from the cell surface of cTEC. Taken together, these results suggest that there are substantial differences in the antigen-presenting pathways of cTEC and mTEC, and these difference might be responsible for T cell selection events in the thymus.

Animals↗
PubMed1996

Fracture damage of embryos and its prevention during vitrification and warming.

The frequency of fracture damage in mouse blastocysts was examined by repeated cycles of vitrification and warming. Mouse blastocysts suspended in a solution of ethylene glycol, Ficoll, and sucrose in a straw were plunged into liquid nitrogen either directly (rapidly) or after holding them in liquid nitrogen vapor for 3 min or more (moderately). Vitrified samples were warmed by plunging them into 25 degrees C water either immediately (rapidly) or after holding in air for 5-30 s (moderately). Warmed straws were recooled and rewarmed up to 9 times, to exaggerate the effect of cooling and warming. When embryos were cooled and warmed rapidly once, the incidence of the zona damage was only 1.2%, and 91% of recovered embryos reexpanded in culture. However, with repeated rapid cooling and warming, the incidence of zona damage increased, reaching 75% after 10 vitrifications; survival also dropped. When embryos were subjected to 10 cycles of moderate cooling and moderate warming with 15 or 30 s of suspension in air, 100% of the embryos had intact zonae. On the other hand, with moderate cooling followed by rapid warming or with rapid cooling followed by moderate warming, 41 and 16% of embryos had damaged zona, respectively, after 10 vitrifications. Therefore, fracture damage occurs during both cooling and warming, but it can be prevented completely by employing somewhat slower rates of cooling and warming. Furthermore, a high survival rate (88%) after 10 cycles of moderate cooling and moderate warming with 15 s of suspension in air indicates that vitrification, melting, or temperature fluctuation per se do not affect embryonic survival.

Animals↗
PubMed1996

Regulation of calcium release channel in sarcoplasmic reticulum.

In this review, we summarized the results obtained mainly by flux measurements through Ca2+ channel in HSR vesicles. The Ca2+ channel has a large pore which passes not only divalent cations such as Ca2+, Mg2+, and Ba2+ and monovalent cations such as Na+, K+, and Cs+, but also large ions such as choline and tris. The permeation rates of choline and glucose through the Ca2+ channel were measured quantitatively by the light scattering method. The slow permeation of such molecules may reflect the structure of pores since the permeation process is the rate-limiting step for such large molecules. Neutral molecules such as glucose became permeable in the presence of submolar KCl, which suggests that pore size of the channel becomes larger in KCl. The apparent permeation rates of Ca2+ and Mg2+ obtained from the flux measurement were the same, although their single-channel conductances were different. This discrepancy was explained by the fact that flux measurements reflects the open rate of the channel. Thus, complementarity between the flux measurement and single-channel recording was demonstrated. From the effects of K+ on the action of regulators on Ca2+ channel, it was suggested that the Ca2+ channel has many binding sites for activators and inhibitors. There are two kinds of Ca2+ binding sites for activation and inhibition. Activation sites for Ca2+, caffeine, and ATP are different and inhibition sites for Ca2+ and procaine are different. The binding sites for ruthenium red and Mg2+ are the same as the activation and/or inhibition sites for Ca2+. Ryanodine-treated Ca2+ channel became permeable to glucose even in the absence of KCl. The conformational state of the channel opened by ryanodine is different from that opened by Ca2+, caffeine, and ATP. The maximal flux rates of choline and glucose induced by ryanodine were smaller than those attained by caffeine and ATP. This result is consistent with the observation obtained by single-channel recording; the maximal value of single-channel conductance after ryanodine treatment becomes 40-50% of the value before the treatment. It is likely that the radius of the pore opened by ryanodine is smaller than that opened by Ca2+, caffeine, or ATP. The flexibility of the channel may be decreased in the open locked state induced by ryanodine. The Ca2+ response to open the channel by micromolar Ca2+ was lost when calsequestrin was released from the vesicles. It is possible that calsequestrin acts as an endogenous regulator of Ca2+ channel through triadin in excitation-contraction coupling.

Animals↗
PubMed1996

Transformation of severe aplastic anemia into acute myeloblastic leukemia with monosomy 7.

A cytogenetically normal man with severe aplastic anemia was treated with granulocyte colonystimulating factor (G-CSF), erythropoietin (EPO), cyclosporin A, anti-thymocyte globulin, and interleukin-6 (IL-6), which resulted in a gradual improvement in his neutrophil count and hemoglobin level. After 2 years of the therapy, monosomy 7 was detected during cytogenetic analysis of his bone marrow, which evolved during a period of 5 months into acute myeloblastic leukemia. An in vitro proliferation assay of cytokine responses showed that leukemic blasts were sensitive only to G-CSF, and not to EPO or IL-6. Although allogeneic bone marrow transplantation from an HLA-matched unrelated donor was carried out in the non-remission stage, the patient died of systemic fungal infection on day 25, without any evidence of hematological engraftment. As long-term use of cytokines and immunomo-suppressants in patients with severe aplastic anemia may induce or hasten the onset of a malignant transformation, careful attention must be paid to clonal evolution. Due to the poor prognosis of secondary myelodysplasia and leukemia, allogeneic bone marrow transplantation for such patients must be carried out early in the course of the disease.

Adult↗
PubMed1996

Thymocyte-directed enhancement of apoptosis via soluble factor(s) derived from a cortical and a medullary thymic epithelial cell line.

Apoptosis of murine thymocytes was examined either in intact fetal thymus lobes or in thymus cell suspensions, both cultured alone or in the presence of either a cortical (TEC 1.4) or a medullary (TEC 2.3) thymic epithelial cell line. Both TECs induced a pronounced increase of apoptosis in 24-h cultivated single thymus cell suspensions but not in spleen or bone marrow cell cultures. Co-culture of thymocytes with murine fibroblasts did not enhance apoptosis of the thymus cells. A similar enhancement of thymocyte apoptosis was observed with dialysed culture supernatants derived from both TEC lines, the active component(s) having a molecular weight of > 30 kDa. In contrast, the cortical TEC 1.4 had a pronounced apoptosis inducing effect on intact fetal thymus lobes cultivated for six days, whereas the medullary TEC 2.3 had only a marginal influence. TEC 1.4 also induced a significant alteration in the ratio of CD4+CD8+ to CD4-CD8- cells. It is concluded that both the cortical and medullary epithelial cell lines are able to induce thymocyte apoptosis but that a large proportion of the cells within the intact thymus stroma is refractory to the respective signal(s) of the medullary epithelial cell line.

Animals↗
PubMed1996

GTP-binding protein activation underlies LTP induction by mast cell degranulating peptide.

Mast cell degranulating peptide (MCD) induces long-term potentiation (LTP) in the CA1 region of the hippocampus. MCD has been shown to bind to a voltage-dependent A-type potassium channel with high-affinity (less than 1 nM). However, the concentration necessary to induce LTP is more than 500 nM, suggesting that some other functions of MCD are also fundamental to LTP induction. The concentration of MCD required for LTP induction was greatly reduced by preactivating G proteins. This fact suggests that G protein activation by MCD also plays an important role in LTP induction. MCD-binding proteins were purified from rat brain. G proteins were found to exist in a non-denatured state in this affinity-purified fraction. When reconstituted into a planar lipid bilayer membrane, a potassium-selective and voltage-dependent current could be observed. This channel was blocked by MCD at a high concentration equal to the effective concentration for G protein activation. Addition of GTP-gamma-S significantly blocked the reconstituted current. Thus, we identified a pathway for LTP induction by MCD in which high concentrations of MCD activate G protein which in turns leads to blocking of a potassium channel.

Adenosine Diphosphate Ribose↗
PubMed1996

Interleukin-12 prevents antigen-induced eosinophil recruitment into mouse airways.

Interleukin-12 (IL-12) is a key cytokine that promotes Th1-type cell-mediated immunity and inhibits Th2-type responses. We have previously shown that antigen-induced eosinophil recruitment into the airways of sensitized mice is mediated by Th2-type CD4+ T cells that produce IL-5. Therefore, to determine whether IL-12 regulates antigen-induced eosinophil recruitment into the airways, we studied the effect of recombinant murine IL-12 on antigen-induced eosinophil infiltration into the tracheas of sensitized mice, and also the effect of IL-12 on IL-5 and interferon-gamma (IFN-gamma) levels in bronchoalveolar lavage fluid (BALF) from the mice. The intraperitoneal administration of recombinant IL-12 (rIL-12) inhibited antigen-induced eosinophil infiltration into the mouse trachea in a dose-dependent manner. The administration of rIL-12 suppressed IL-5 levels but enhanced IFN-gamma levels in the BALF of the mice after antigen inhalation. The administration of rIL-12 also decreased in vitro antigen-induced IL-4 and IL-5 production, but not IFN-gamma production, in spleen cells of the mice. Furthermore, pretreatment with anti-IFN-gamma monoclonal antibody prevented the IL-12 inhibition of antigen-induced eosinophil infiltration into the tracheas of the mice. These results indicate that IL-12 downregulates antigen-induced eosinophil recruitment into the airways by inhibiting IL-5 production in sensitized animals.

Animals↗
PubMed1996

Analysis of multiple conductance states observed in Ca2+ release channel of sarcoplasmic reticulum.

Both slowly and rapidly fluctuating currents were observed after incorporating a heavy sarcoplasmic reticulum (HSR) vesicle or a purified ryanodine receptor (RyR) of rabbit skeletal muscle into a lipid bilayer. The responses to the cis side Ca2+, ruthenium red and ryanodine confirmed that both were the currents through one Ca2+ release channel. From the analysis of conductance states, RyR is supposed to have two different configurations. The current through one configuration has a high reversal potential (HRP) (-18 mV) and that through another one has a low reversal potential (LRP) (-11 mV). The current with HRP fluctuates rapidly but the current with LRP always fluctuates slowly. From the analysis of both rapidly and slowly fluctuating currents, it was shown that there are four pores in RyR. Among the conductance states of the slowly fluctuating current with LRP, the conductance of the 4OP (four opened pores) state was smaller than four times that of 1OP (one opened pore). To explain this fact, we proposed a model of the channel, a large central pore in series with four small parallel pores. The calculation according to the model has a good fit with the bilayer measurement.

Animals↗
PubMed1996

Cryopreservation of zona-hatched mouse blastocysts.

Experiments were conducted to determine the conditions for successful and efficient cryopreservation of hatched mouse blastocysts, using simple vitrification procedures. Hatched blastocysts were obtained by culture of morulae in vitro. Vitrification solutions used were EFS40 and GFS40, which were 40% (v/v) ethylene glycol and 40% (v/v) glycerol, respectively, diluted in PB1 medium containing 30% Ficoll (w/v) and 0.5 mol sucrose l-1. In the one-step method, embryos were directly exposed to the vitrification solutions at 25 degrees C for 0.5 or 2 min; in the two-step method, embryos were equilibrated with a dilute (10-20%, v/v) ethylene glycol or glycerol solution for 5-10 min, before a 0.5 min exposure to EFS40 or GFS40, respectively. They were then vitrified in liquid nitrogen. When the embryos were vitrified in EFS40, the post-warming survival rates, assessed by the re-expansion of the blastocoel during 16 h of culture, were higher in embryos that had hatched from the zona earlier (120-132 h after hCG) than in those hatched later (142-150 h after hCG); however, the highest survival rate was only 65%, which was obtained by a one-step method. When embryos were vitrified in GFS40, a high survival rate (89-94%) was obtained especially by the two-step methods. Vitrified blastocysts developed into live young just as well as did fresh blastocysts; survival was highest after transfer to recipients on day 3 or day 4 of pseudopregnancy. These findings show that hatched mouse blastocysts can be successfully cryopreserved by a simple vitrification method, and that a glycerol-based vitrification solution is more suitable than the corresponding ethylene glycol-based solution for the vitrification, probably because slower permeation of glycerol avoids toxic injury.

Animals↗
PubMed1996

Antitumor effect in cyclosporine A- or FK506-treated mice after syngeneic bone marrow transplantation.

We investigated the possibility for induction of graft-versus-tumor (GVT) effects in cyclosporine A (CsA)- or FK506 (FK)-treated DBA/2 mice after syngeneic bone marrow transplantation (BMT). For in vitro assays of spleen cells, the CsA-treated mice had more enhanced cytotoxic activity against YAC1 and P388, while the FK-treated animals had more against P815, YAC1, and P388. IL-4 mRNA expression was detected in spleen cells of the FK-treated mice and IL-6 mRNA expression was clearly detected in both the treated groups. Concerning GVT effects, FK had more pronounced immunostimulatory potential than CsA in this experimental setting using DBA/2 mice. In tumor-loading in vivo experiments, we could not show any antitumor effect on survival. However, this immunostimulation could be expected to eradicate the minimal residual disease after autologous BMT and autologous peripheral blood stem cell transplantation.

Actins↗
PubMed1996

Expression of erythroid-specific genes in megakaryoblastic disorders.

Currently available data indicate that erythroid and megakaryocytic differentiation pathways are closely related to each other, and there may exist progenitor cells common to those two lineages may exist. Acute megakaryoblastic leukemia (AML-M7) and transient myeloproliferative disorder in Down's syndrome (TMD) are characterized by rapid growth of abnormal blast cells which express megakaryocytic markers. These blast cells express lineage-specific transcription factors such as GATA-1 common to these lineages and frequently express erythroid-specific mRNAs such as gamma-globin and erythroid delta-aminolevulinate synthase (ALAS-E), indicating that most of the blasts in M7 and TMD cases have erythroid and megakaryocytic phenotypes. These results suggest that blasts in M7 and TMD may correspond to progenitors of both erythroid and megakaryocytic lineages.

DNA-Binding Proteins↗