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Biomedical subjects

A Tabuchi

Publications and source records attributed to A Tabuchi.

At least 19 recordsLinked to original sources
PubMed2004

[Surgical treatment of thymic carcinomas].

Five cases of surgically treated thymic carcinoma are reported. The patients (4 men and a woman) ranged in age from 46 to 76 years old with a mean of 64.6. Four patients were asymptomatic and an abnormal shadow on X-ray films was noted. One remaining patient suffered from hoarseness. One patient had stage II disease and the others had stage III. Surgical tumor resection was performed in all cases. Only 1 patient among the 5 underwent a successful complete resection. Histological examinations of the resected specimens revealed squamous cell carcinoma of thymus. Four specimens were poorly differentiated and 1 is moderately differentiated carcinoma. All patients received radiation therapy post operatively. Three patients are alive without any recurrence 6, 8 and 109 months after the surgery. Thymic carcinomas are frequently invasive or metastatic at the time of diagnosis. But poorly differentiated group, in squamous cell carcinoma, mucoepidermoid carcinoma and besaloid carcinoma, are characterized by a low incidence of local recurrence and distant metastasis. They also have a good sensitivity for the radiation. Therefore complete surgical resection combined with postoperative radiation therapy should be a choice in treating thymic carcinomas. We considered that complete resection and postoperative radiation therapy is a curative therapy for thymic carcinomas.

Aged↗
PubMed2001

Identification of protein kinase Calpha as an essential, but not sufficient, cytosolic factor for Ca2+-induced alpha- and dense-core granule secretion in platelets.

Upon activation, platelets release many active substances. Here, we have analyzed the mechanism governing Ca(2+)-induced secretion of von Willebrand factor stored in alpha-granules and 5-hydroxytryptamine in dense-core granules in permeabilized human platelets. Both secretions were dependent on ATP and cytosol. An essential factor for both granule secretions was purified from rat brain cytosol and identified to be protein kinase Calpha (PKCalpha) by partial amino acid sequencing. Purified PKCalpha efficiently stimulated both secretions in the presence of cytosol, whereas PKCalpha alone did not support the secretion of either type of granules, suggesting that PKCalpha is not a sufficient factor. Finally, in human platelet cytosol fractionated by a gel filtration column, the stimulatory activity for dense-core granule secretion paralleled with the concentration of PKC, suggesting that PKC could also be such a stimulatory factor in platelet cytosol. Thus, we identified PKCalpha as an essential, but not sufficient, cytosolic factor for the Ca(2+)-induced secretions of both alpha- and dense-core granules in platelets.

Adenosine Triphosphate↗
PubMed2001

Novel splice variants of PACAP gene in mouse cerebellar granule cells.

The mouse pituitary adenylate cyclase activating polypeptide (PACAP) gene consists of two alternative exons (1A and 1B) and four exons including the coding region. By the usage of alternative exons, three transcripts can be produced. In this report, however, we found that at least five preproPACAP transcripts, including two novel types, were produced in mouse cerebellar granule cells (CGCs) and their expression was induced by the Ca2+ influx through L-type voltage-dependent Ca2+ channels. The splicing occurred between the 3'-donor site of exon 1A and the two novel internal 5'-acceptor sites of exon 1B. These findings suggest that preproPACAP transcripts are produced by the complicated usage of the 5'-untranslated region in an activity-dependent manner.

Alternative Splicing↗
PubMed2001

Small GTPase Rho regulates thrombin-induced platelet aggregation.

Platelets play essential roles in hemostasis and thrombosis by aggregating with each other. However, the molecular mechanism governing platelet aggregation is not yet fully understood. Here, we established an assay system using platelets permeabilized with streptolysin-O to analyze mechanism of the thrombin-induced aggregation, focusing upon a controversial issue in the field whether small GTPase Rho regulates the aggregation. Incubation of the permeabilized platelets with Rho GDP-dissociation inhibitor, an inhibitory regulator for Rho family GTPases, extracted Rho family proteins extensively from the plasma and intracellular membranes, and inhibited the thrombin-induced aggregation. Incubation of the permeabilized platelets with botulinum exoenzyme C3, which specifically inhibits Rho function by ADP-ribosylating it, abolished the thrombin-induced aggregation. Thus, Rho is involved in thrombin-induced aggregation of platelets.

ADP Ribose Transferases↗
PubMed2001

Involvement of endogenous PACAP expression in the activity-dependent survival of mouse cerebellar granule cells.

Membrane depolarization causes Ca2+ influx through L-type voltage-dependent calcium channels (L-VDCC), which promotes the activity-dependent survival of mouse cerebellar granule cells (CGCs). Although exogenously added pituitary adenylate cyclase activating polypeptide (PACAP) is effective in promoting the survival of CGCs, it is unknown whether PACAP is synthesized in CGCs and involved in the activity-dependent survival of CGCs. In this study, we found that the PACAP gene was activated in depolarized CGCs cultured at 25 mM KCl (high K+), independently of de novo protein synthesis. In addition, the PACAP immunoreactivity increased through the activation of L-VDCC in depolarized CGCs, indicating that PACAP is concomitantly produced with PACAP mRNA in an activity-dependent manner. Exogenously added PACAP attenuated the apoptosis of CGCs through a specific interaction with PACAP receptors. Furthermore, a PACAP receptor antagonist, PACAP(6-38), reduced the survival of CGCs at high K+. These findings indicate that endogenous PACAP production induced by Ca2+ signals exerts a survival effect on CGCs via PACAP receptors, which, at least in part, accounts for the activity-dependent survival of CGCs.

Actins↗
PubMed2001

A new type of endo-xyloglucan transferase devoted to xyloglucan hydrolysis in the cell wall of azuki bean epicotyls.

A new type of xyloglucan-degrading enzyme was isolated from the cell wall of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) epicotyls and its characteristics were determined. The enzyme was purified to apparent homogeneity by Concanavalin A (Con A)-Sepharose, cation exchange, and gel filtration columns from a cell wall protein fraction extracted with 1 M sodium chloride. The purified enzyme gave a single protein band of 33 kDa on SDS-PAGE. The enzyme specifically cleaved xyloglucans and showed maximum activity at pH 5.0 when assayed by the iodine-staining method. An increase in reducing power in xyloglucan solution was clearly detected after treatment with the purified enzyme. Xyloglucans with molecular masses of 500 and 25 kDa were gradually hydrolyzed to 5 kDa for 96 h without production of any oligo- or monosaccharide with the purified enzyme. The purified enzyme did not show an endo-type transglycosylation reaction, even in the presence of xyloglucan oligosaccharides. Partial amino acid sequences of the enzyme shared an identity with endo-xyloglucan transferase (EXGT) family, especially with xyloglucan endotransglycosylase (XET) from nasturtium. These results suggest that the enzyme is a new member of EXGT devoted solely to xyloglucan hydrolysis.

Cell Wall↗
PubMed2001

Molecular dissection of alpha- and dense-core granule secretion of platelets.

Upon activation, platelets release many active substances stored in alpha- and dense-core granules. However, the molecular mechanisms governing the regulated exocytosis are not yet fully understood. We have established an assay system using streptolysin-O-permeabilized platelets to analyze the Ca2+-induced secretions of von Willebrand factor stored in alpha-granules and [3H]5-hydroxytryptamine (5-HT) in dense-core granules. Using the assay, we found that small GTPase Rab4 regulates alpha-, but not dense-core, granule secretion in platelets. Furthermore, we purified a cytosolic essential protein and currently are analyzing its function.

Blood Platelets↗
PubMed2001

[Studies on kinetic viscoelasticity of slow muscle fibers--2. Dynamic stiffness changes studied by quick release method and frequency response method].

PURPOSE: To evaluate the mechanical properties of slow fibers and fast fibers which make up the extraocular muscles in rabbits. SUBJECTS AND METHOD: I studied the contractile properties and viscoelastic properties of the superior rectus muscle(SR) and the retractor bulbi muscle (RB) of rabbits using the quick release method and the frequency response method. RESULTS: In the quick release method, isometric tension transients were slower in the SR than in the RB. In the frequency response method, the muscle length is perturbed sinusoidally to measure kinetic viscoelasticity. In resting muscle, dynamic stiffness was not changed with increasing frequency. In contracted muscle, dynamic stiffness was increased with increasing frequency, and the rate of increase was greater in the SR than in the RB. CONCLUSION: It was concluded that the viscoelasticity of the activated cross bridge is greater in slow fibers than in fast fibers.

Animals↗
PubMed2001

[Examination of eye position after strabismus surgery in Kawasaki Medical School Hospital].

PURPOSE: To examine the factors which affect changes in the position of the eyes following the strabismus surgery. METHODS: The postoperative position of 240 eyes with concomitant strabismus was examined. The factors which seemed to have an effect on the position of the eyes were enumerated, and a logistic regression analysis of the results was done. RESULTS: In comparison with esotropia, in exotropia the eyes showed a tendency to return gradually to a normal position. There was no remarkable improvement in stereoscopic vision following strabismus surgery. Based on the standards of the Japanese Association of Strabismus and Amblyopia [the cure standard for strabismus], the results of strabismus surgery were as follows: Grade 1(cosmetically satisfactory) was mainly observed for esotropia, and Grade 3(good) for exotropia. The factors which had a significant effect on the postoperative position of the eyes were as follows: esotropia amblyopia, muscle movement, and operative methods; exotropia: retinal correspondence, operative methods, and the necessity of inferior oblique muscle surgery. CONCLUSIONS: There was little correction of the position of the eyes. In individual cases, the factors which affect position of eyes were examined, and it was considered necessary to increase the amount of correction. Age is a factor which has an effect, but the effect on esotropia and exotropia is small.

Adolescent↗
PubMed2000

Small GTPase Rab4 regulates Ca2+-induced alpha-granule secretion in platelets.

Upon activation, platelets release many active substances stored in alpha- and dense-core granules. However, the molecular mechanisms governing regulated exocytosis are not yet fully understood. Here, we have established an assay system using permeabilized platelets to analyze the Ca(2+)-induced exocytosis of both types of granules, focusing on RabGTPases. Incubation with Rab GDP dissociation inhibitor, an inhibitory regulator of RabGTPases, reduced membrane-bound RabGTPases extensively, and caused strong inhibition of the Ca(2+)-induced secretion of von Willebrand factor (vWF) stored in alpha-granules, but not that of [(3)H]5-hydroxytryptamine (5-HT) in dense-core granules. Specifically, Rab4 co-fractionated with vWF and P-selectin (an alpha-granule marker) upon separation of platelet organelles by density gradient centrifugation. Incubation of the permeabilized platelets with cell extracts expressing the dominant negative mutant of His-tagged Rab4S22N, but not with those of similar mutant His-Rab3BT36N, inhibited the vWF secretion, whereas neither of the cell extracts affected the [(3)H]5-HT secretion. Importantly, the inhibition of vWF secretion was rescued by depleting the cell extracts of the His-Rab4S22N with nickel beads. Thus, in platelets, the regulatory mechanisms governing alpha- and dense-core granule secretions are distinct, and Rab4 is an essential regulator of the Ca(2+)-induced exocytosis of alpha-granules.

Bacterial Proteins↗
PubMed2000

Differential activation of brain-derived neurotrophic factor gene promoters I and III by Ca2+ signals evoked via L-type voltage-dependent and N-methyl-D-aspartate receptor Ca2+ channels.

Although the brain-derived neurotrophic factor (BDNF) gene is activated by the intracellular Ca(2+) signals evoked via Ca(2+) influx into neurons, little is known about how the activation of alternative BDNF gene promoters is controlled by the Ca(2+) signals evoked via N-methyl-d-aspartate receptors (NMDA-R) and L-type voltage-dependent Ca(2+) channels (L-VDCC). There is a critical range in the membrane depolarization caused by high K(+) concentrations (25-50 mm KCl) for effective BDNF mRNA expression and transcriptional activation of BDNF gene promoters I and III (BDNF-PI and -PIII, respectively) in rat cortical culture. The increase in BDNF mRNA expression induced at high K(+) was repressed not only by nicardipine, an antagonist for L-VDCC, but also by dl-amino-5-phosphonovalerate, an antagonist for NMDA-R, which was supported by the effects of antagonists on the Ca(2+) influx. Although the promoter activations at 25 and 50 mm KCl were different, BDNF-PIII was activated by either the Ca(2+) influx through NMDA-R or L-VDCC, whereas BDNF-PI was predominantly by the Ca(2+) influx through L-VDCC. Direct stimulation of NMDA-R supported the activation of BDNF-PIII but not that of BDNF-PI. Thus, the alternative BDNF gene promoters responded differently to the intracellular Ca(2+) signals evoked via NMDA-R and L-VDCC.

2-Amino-5-phosphonovalerate↗
PubMed2000

Dynamic topography of pattern visual evoked potentials (PVEP) in psychogenic visual loss patients.

We investigated to measure the objective visual acuity using pattern visual evoked potentials (PVEP) to help the diagnosis with psychogenic visual loss (PVL) who ranged in age from 7 to 14 years old. Pattern stimuli consisted of black and white checkerboard patterns (39, 26, 15 and 9') with a visual angle of 8 degrees and a contrast level of 15%. The pattern reversal frequency was 0.7 Hz. This resulted in an average of 100 PVEP per session. Visual acuity of 0.1 was consistent with the 39' pattern, 0.2 with the 26' pattern, 0.5 with the 15' pattern, and 1.0 with the 9' pattern. As the results, five PVL patients could measure visual acuity with this method in the present study. The PVEP is useful in evaluating the visual acuity and helped to diagnose the PVL patients. In addition we used the dynamic topography to study the difference in the results of the PVEP. The dynamic topography obtained from the results of the PVEP was analyzed. The flow type of the P100 component diverged into three types (separated type, hollow type and localized type) in the PVL patients and the normal children. The localized type was observed in 59.1% of normal children and in 56.3% of PVL patients. While the separated type was shown in 6.8% of normal children and in 8.3% of PVL patients. There were not significant differences between the PVL patients and the normal children in each type.

Adolescent↗
PubMed2000

Growth regulation mechanisms in higher plants under microgravity conditions - changes in cell wall metabolism.

During Space Shuttle STS-95 mission, we cultivated seedlings of rice (Oryza sativa L. cv. Koshihikari and cv. Tan-ginbozu) and Arabidopsis (Arabidopsis thaliana L. cv. Columbia and cv. etr1-1) for 68.5, 91.5, and 136 hr on board, and then analyzed changes in the nature of their cell walls, growth, and morphogenesis under microgravity conditions. In space, elongation growth of both rice coleoptiles and Arabidopsis hypocotyls was stimulated. Also, the increase in the cell wall extensibility, especially that in the irreversible extensibility, was observed for such materials. The analyses of the amounts, the structure, and the physicochemical properties of the cell wall constituents indicated that the decreases in levels and molecular masses of cell wall polysaccharides were induced under microgravity conditions, which appeared to contribute to the increase in the wall extensibility. The activity of certain wall enzymes responsible for the metabolic turnover of the wall polysaccharides was increased in space. By the space flight, we also confirmed the occurrence of automorphogenesis of both seedlings under microgravity conditions; rice coleoptiles showed an adaxial bending, whereas Arabidopsis hypocotyls elongated in random directions. Furthermore, it was shown that spontaneous curvatures of rice coleoptiles in space were brought about uneven modifications of cell wall properties between the convex and the concave sides.

Arabidopsis↗
PubMed2000

Repression of activity-dependent c-fos and brain-derived neurotrophic factor mRNA expression by pyrethroid insecticides accompanying a decrease in Ca(2+) influx into neurons.

Permethrin, a type I pyrethroid insecticide, is known to affect sodium channels of neurons and prolong sodium currents. On the other hand, the expression of brain-derived neurotrophic factor (BDNF) and c-fos genes is activated through Ca(2+) influx into neurons, in an activity-dependent manner. In this study, therefore, we investigated whether permethrin influenced the Ca(2+) signal-induced expression of these genes. In primary culture of mouse cerebellar granule cells (CGCs), stimulation with veratridine, a potent agonist for sodium channels, which causes membrane depolarization in neurons, induced c-fos and BDNF mRNA expression accompanying the Ca(2+) influx into neurons. Pretreatment with permethrin at doses nontoxic to CGCs repressed the induction of these genes dose dependently, with trans-permethrin more potent than cis-permethrin. Consistent with this, the increase in Ca(2+) influx caused by veratridine was repressed by permethrin. The membrane depolarization induced by elevating the potassium (K(+)) concentration in medium (high K(+)) caused the activation of c-fos and BDNF genes, which was also repressed by permethrin. Immunoblotting analysis of c-Fos and a gel-mobility assay of AP-1 DNA-binding activity supported the decrease in c-Fos synthesis in permethrin-treated CGCs. The type II pyrethroid cypermethrin also affected the expression of these genes but less effectively than permethrin. Thus, pyrethroids inhibit the activity-dependent gene expression in neurons.

Animals↗
PubMed1999

Silencer-mediated repression and non-mediated activation of BDNF and c-fos gene promoters in primary glial or neuronal cells.

Although the neuron-restrictive silencer element (NRSE/Regard) has been shown to function as a negative-acting DNA regulatory element to prevent the expression of neuron-specific genes in non-neuronal cells, little is known about its silencing effect on transcription in primary glial cells nor its effect on transcriptional activation in primary neurons. By DNA transfection in primary cultures of rat cortical neuronal or glial cells, we investigated the effect of NRSE on transcription mediated by the BDNF promoter I or c-fos promoter to which NRSE sequences derived from the SCG10 gene were linked. Transfection of plasmid DNAs to NIH3T3 fibroblasts resulted in a marked repressive effect of NRSE on BDNF promoter I- or c-fos promoter-mediated transcription. In primary neuronal cells, however, NRSE did not repress the basal promoter activities of BDNF and c-fos genes and allowed the transcriptional activation of these genes induced by membrane depolarization although NRSE slightly reduced the magnitude of BDNF promoter I activation. In contrast to neuronal cells, a marked repression of basal promoter activities of both genes was detected in primary glial culture and a two base pair-mutation of NRSE partially recovered the repression. These results indicate that NRSE negatively acts on its linked promoters in primary glial cells and does not interfere an activation of linked promoters in neuronal cells.

3T3 Cells↗
PubMed1999

Coactivation of secretogranin-II and BDNF genes mediated by calcium signals in mouse cerebellar granule cells.

In primary culture of mouse cerebellar granule cells, the brain-derived neurotrophic factor (BDNF) gene is activated in an activity-dependent manner, accompanying Ca2+ influx into neurons through voltage-dependent calcium channels (VDCCs). In this study, we investigated the inducibility of secretogranin-II (Sg-II) gene in terms of Ca2+ signals evoked via VDCCs, by a comparison with BDNF and c-fos genes. Deprivation and subsequent induction of membrane depolarization by lowering and reelevating the extracellular concentration of potassium chloride (KCl), respectively, led to an decrease and then an increase in the Sg-II, BDNF and c-fos mRNA expression. The increase in Sg-II mRNA expression was detected as early as but was slower than that of BDNF one. The increase in Sg-II mRNA expression was induced depending upon the extracellular Ca2+ and inhibited by nicardipine, indicating a requirement of Ca2+ influx through VDCCs for the Sg-II as well as BDNF gene induction. Inhibition of de novo protein synthesis by cycloheximide did not affect the Sg-II induction. The response of Sg-II gene to the changes in extracellular KCl concentration was the same as that of BDNF but different from that of c-fos gene. Thus, Sg-II gene is coactivated with BDNF gene in response to the intracellular Ca2+ signals evoked via Ca2+ influx through VDCCs.

Animals↗
PubMed1999

[Clinical results of supratentorial astrocytoma grade II].

At present, there is no consensus concerning the treatment of low-grade gliomas. The authors conducted a retrospective review of surgically treated, histologically verified cases of supratentorial astrocytomas of grade II to evaluate the results of current treatment methods. Thirty-seven patients, 23 males and 14 females, treated from April, 1977 through March, 1997 were analyzed. Median patient age was 36 years (range 2-69 years). All patients were diagnosed by surgical specimens. Thirty were fibrillary, and three were gemistocytic astrocytomas. There were 13 total resections, 7 subtotal resections, 10 partial resections. Of the remaining 7, diagnosis was obtained by stereotactic biopsy. Twenty patients were irradiated and two received chemotherapy. Follow-up information was obtained for 33 patients. The follow-up time ranged from 4 months to 246 months (mean, 9 years). Overall survival rates at 5 and 10 years for the entire treated group were 71% and 57% respectively. Total and subtotal resections were significantly associated with longer survival time, the 5- and 10-year survival rates were 93% and 67%, respectively. They were 40% and 40% in patients with partial resection or needle biopsy. Patients with gemistocytic astrocytoma had a poor prognosis with a median survival of 44.5 months. The influence of radiotherapy was not obvious: 92 and 69% of patients were alive at 5 and 10 years respectively without radiotherapy. The extent of surgery and histological type were by far the most important factors in predicting length of survival. The importance of an accurate histologic diagnosis and a gross total resection is emphasized.

Adolescent↗