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Biomedical subjects

H Osada

Publications and source records attributed to H Osada.

At least 55 records · Page 3Linked to original sources
PubMed2000

Involvement of protein kinase C-regulated ceramide generation in inostamycin-induced apoptosis.

Activation of caspases is commonly involved in the apoptosis induced by various anticancer drugs. However, the upstream events leading to the activation of caspases seem to be specific to each anticancer drug. In the present study, we examined the possible involvement of protein kinase C (PKC) and ceramide generation in caspase-3(-like) protease activation induced by inostamycin, a phosphatidylinositol synthesis inhibitor. Treatment of cells with 12-O-tetradecanoyl phorbol-13-acetate (TPA), an activator of PKC, suppressed the release of cytochrome c from mitochondria and the activation of caspase-3(-like) proteases in inostamycin-treated cells, but not in other anticancer drug-treated cells. Inostamycin induced the elevation of intracellular ceramide levels, and fumonisin B1, an inhibitor of ceramide synthase, inhibited inostamycin-induced cytochrome c release, caspase-3(-like) protease activation, and apoptosis. Moreover, TPA also inhibited inostamycin-induced ceramide synthesis. Taken together, our results suggest that inostamycin-induced apoptosis is mediated by PKC-regulated ceramide generation, leading to the activation of a caspase cascade.

Anti-Bacterial Agents↗
PubMed2000

MT-21 is a synthetic apoptosis inducer that directly induces cytochrome c release from mitochondria.

We reported previously that a synthetic compound, MT-21, induced apoptosis by activating c-Jun-NH2-terminal kinase via the Krs/MST protein, which is activated by caspase-3 cleavage dependent on reactive oxygen species production. Here we examine the activation mechanism of caspase-3, an important cysteine aspartic protease, during MT-21-induced apoptosis. We found that MT-21 activated caspase-3 via caspase-9, but not via caspase-8. In addition, MT-21 induced the release of cytochrome c from the mitochondria that is necessary to activate caspase-9, and this release occurred before a change in membrane potential. This initiation process of MT-21-induced apoptosis was suppressed by overexpression of Bcl-2, which is known to prevent cells from undergoing apoptosis in response to a variety of stimuli. Moreover, when we treated mitochondria isolated from the cells with MT-21, the direct release of cytochrome c from the mitochondria was observed, whereas this effect was not observed in the mitochondria isolated from cells that overexpressed Bcl-2. Other apoptosis-inducing agents known to induce apoptosis via cytochrome c release from the mitochondria failed to release cytochrome c directly from isolated mitochondria. These findings indicate that MT-21 is a possible candidate antitumor agent that is able to induce apoptosis via the direct release of cytochrome c from the mitochondria.

Antineoplastic Agents↗
PubMed2000

Histological type-selective, tumor-predominant expression of a novel CHK1 isoform and infrequent in vivo somatic CHK2 mutation in small cell lung cancer.

Inactivation of p53, which represents the most prevalent genetic alteration in lung cancer, has been shown to play a crucial role in the acquisition of genomic instability. We examined 44 lung cancer specimens to search for mutations in the CHK1 and CHK2 genes, which have been suggested to play roles in regulating p53 after DNA damage. We found that the CHK2 gene was somatically mutated in lung cancer in vivo, although at a low frequency, and that a previously undescribed shorter isoform of CHK1 was expressed preferentially in small cell lung cancer in a tumor-predominant manner. Additional studies are warranted to investigate the functional significance of these changes as well as the potential involvement of other components in this important pathway to maintain genomic stability.

Amino Acid Sequence↗
PubMed2000

Heterogeneities in the biological and biochemical functions of Smad2 and Smad4 mutants naturally occurring in human lung cancers.

Smad family members are essential intracellular signaling components of the transforming growth factor-beta (TGF-beta) superfamily involved in a range of biological activities. The loss of sensitivity to TGF-beta is frequent in human lung cancers and inactivation of Smad family members are thought to play important roles in disruption of TGF-beta signaling. In the study presented here, we characterized the biological and biochemical functions of six Smad2 and Smad4 mutants, which we previously identified in human lung cancers. All mutant Smad2 and Smad4 were in fact found to be defective in transmitting growth inhibitory signals originating from TGF-beta and incapable of activating Smad/hFAST-1-mediated transcription. Transcriptional activation of plasminogen activator inhibitor type 1 (PAI-1) was impaired in four of the six mutants due to the defects in homo- and/or hetero-oligomerization with wild-type Smads. In contrast, the remaining two Smad mutants showed a modest reduction in the PAI-1 transcriptional activation and apparently retained the ability to oligomerize with wild-type Smads. Significant loss of growth inhibition and Smad/hFAST-1-mediated transcriptional activation by all of the six mutants suggested that Smad mutants are indeed functionally impaired Smad mutations and may play a role in lung tumorigenesis. Moreover, the present findings suggest that in addition to the impairment in the homo- and/or hetero-oligomerization, there may be an alternative mechanism producing disruption of TGF-beta signaling, involving hFAST-1-or possibly other transcriptional cofactor(s)-mediated transcriptional activation.

DNA-Binding Proteins↗
PubMed2000

Synthesis and evaluation of tryprostatin B and demethoxyfumitremorgin C analogues.

Tryprostatin B and demethoxyfumitremorgin C are fungal inhibitors of mammalian cell cycle progression at the G(2)/M transition. N-Alkyl derivatives of the L-Trp-L-Pro diketopiperazine were prepared as analogues of tryprostatin B, and two of these were more active than the natural product. A second series of cis- and trans-tetrahydro-beta-carbolines annulated to a diketopiperazine were prepared as analogues of demethoxyfumitremorgin C. The nature of the alkyl substituent, as well as its cis or trans relationship in the tetrahydro-beta-carboline ring, was found to have a significant effect on cytotoxic activity. Small cis-alkyl substituents fall into the demethoxyfumitremorgin C family, whereas bulky benzyl trans compounds appear to act via a different mechanism of action.

Animals↗
PubMed2000

Activation of MST/Krs and c-Jun N-terminal kinases by different signaling pathways during cytotrienin A-induced apoptosis.

We found that antitumor drugs such as cytotrienin A, camptothecin, taxol, and 5-fluorouracil induced the activation of a 36-kDa protein kinase (p36 myelin basic protein (MBP) kinase) during apoptosis in human promyelocytic leukemia HL-60 cells. This p36 MBP kinase, which phosphorylates MBP in an in-gel kinase assay, results from the caspase-3-mediated proteolytic cleavage of MST/Krs protein, a mammalian Ste20-like serine/threonine kinase. Herein the correlation between cytotrienin A-induced apoptosis and the activation of MST/Krs proteins was examined in human tumor cell lines, including leukemia-, lung-, epidermoid-, cervix-, stomach-, and brain-derived cell lines. In cytotrienin A-sensitive cell lines, we observed a strong activation of p36 MBP kinase by cleavage of the C-terminal regulatory domain of full-length MST/Krs proteins by caspase-3. When the kinase-inactive mutant form of MST/Krs protein was overexpressed in cytotrienin A-sensitive HL-60 cells, the cytotrienin A-induced apoptosis was partially inhibited. Because cytotrienin A also activated c-Jun N-terminal kinase, we examined the effect of the expression of dominant negative c-Jun on cytotrienin A-induced apoptosis. The expression of dominant negative c-Jun also partially inhibited cytotrienin A-induced apoptosis. Furthermore, coexpression of kinase-inactive MST/Krs protein and dominant negative c-Jun completely suppressed cytotrienin A-induced apoptosis. These findings suggest that the proteolytic activation of MST/Krs and c-Jun N-terminal kinase activation are involved in cytotrienin A-induced apoptosis in human tumor cell lines.

Antibiotics, Antineoplastic↗
PubMed2000

p62 functions as a p38 MAP kinase regulator.

By screening a HeLa cDNA library to isolate genes encoding p38-regulating proteins, we have isolated two independent clones which encode the binding proteins to p38. We have found that both of these cDNA clones encode p62, first identified as a phosphorylation independent p56(lck) SH2 domain binding protein. Recent studies also indicate that p62 interacts with atypical PKCs to anchor them to intracellular membranes and with RIP to mediate signals to NF-kappaB through atypical PKCs. Moreover, p62 is shown to be involved in the transcriptional regulation via SV40 enhancer and to serve as a coactivator of an orphan nuclear hormone receptor. A coimmunoprecipitation assay shows its enhanced association in HeLa cells after stimulations such as sorbitol and anisomycin. An indirect immunofluorescence study indicates that p62 colocalizes with p38 in the nucleus in response to the stimulation. And in vitro kinase assays using MBP, but not ATF-2, as a substrate show that p62 enhances p38 activities in a dose-dependent manner. Together, these results demonstrate that p62 plays roles not only as an anchor but also as a regulator for the p38 kinase activity.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Prenatal findings in Brachmann-de Lange syndrome.

We present a case of Brachmann-de Lange syndrome, in which prenatal ultrasonographic evaluation demonstrated increased nuchal translucency, early onset of intrauterine growth retardation, and limb abnormalities in the first, second, and third trimester, respectively.

Adult↗
PubMed2000

Experimental tracheal reconstruction with a rotated right stem bronchus.

BACKGROUND: To reconstruct a longer tracheal defect, a safe method other than end-to-end anastomosis is necessary. METHODS: Nine mongrel dogs underwent right thoracotomy. The lobes of the right lung other than the apical lobe were resected, keeping the bronchi in place to be manipulated to extend the right stem bronchial conduit. The trachea was resected for a 10-cartilage-ring length. The modified right stem bronchus was then brought into the mediastinum by rotation in the frontal plane. An end-to-end anastomosis was made. The right apical lobe, once separated, was then reanastomosed end-to-side. Ciliary transport was studied. RESULTS: Eight of the 9 dogs tolerated the surgical procedure well, and the reanastomosed right apical lobe remained well expanded for 1 year or more postoperatively. The inverted segment did not show any cranial ciliary transport movement. CONCLUSIONS: A large tracheal defect more than 10 rings in length can be reconstructed using a rotated right stem bronchus with the right apical lobe reanastomosed. The inverted bronchial segment loses its cranial ciliary transport movement.

Anastomosis, Surgical↗
PubMed2000

Outpatient evaluation and treatment of tubal obstruction with selective salpingography and balloon tuboplasty.

OBJECTIVE: To compare selective salpingography and balloon tuboplasty for the treatment of tubal obstruction. DESIGN: A retrospective evaluation of results of women treated for tubal obstruction by outpatient methods at a single center. SETTING: Tertiary-care, university-affiliated hospital. PATIENT(S): A total of 3,424 infertile women, of whom 418 had bilateral tubal obstruction by hysterosalpingography, treated at Nihon Medical Center from 1982 to 1997. INTERVENTION(S): Women with tubal obstructions who had visual evidence of an intact uterine tubal ostium at hysteroscopy were treated by selective salpingography. If selective salpingography could not establish patency, then transcervical balloon tuboplasty was performed with one of three catheter systems. Patients were followed expectantly for 1 year after treatment. MAIN OUTCOME MEASURE(S): Postoperative tubal patency and overall pregnancy rates (PRs) at 1-year of follow-up. RESULT(S): The overall patency rate was 67.5%, with 30% of these patients conceiving (20.2% of all subjects). Selective salpingography was associated with a 35. 7% patency rate, and 27.3% of these patients conceived. Of the subjects who failed selective salpingography and underwent balloon tuboplasty, 66.2% achieved patency, of whom 33% spontaneously conceived. Balloon tuboplasty was effective in restoring patency in many cases after selective salpingography had failed. Statistically significant differences were found between selective salpingography and balloon tuboplasty and for the different balloon tuboplasty catheters in terms of patency rates, while a trend was seen for PRs. CONCLUSION(S): Many women diagnosed as having tubal obstruction can be treated by outpatient methods that do not require general anesthesia. Achieving patency by these methods is associated with high PRs and avoids the need for assisted reproductive technologies in some cases. Balloon tuboplasty is a more effective treatment than selective salpingography. The choice of balloon tuboplasty catheter system may affect success rates.

Adult↗
PubMed2000

Mutations in the Plk gene lead to instability of Plk protein in human tumour cell lines.

It has been established that mutations in Drosophila Polo cause abnormalities in mitosis. In human cells, maximal Plk activity is reached in the M phase of the cell cycle, and the function of Plk is therefore considered to be required for mitotic cellular events such as spindle formation, chromosome segregation and cytokinesis. Microinjection of anti-Plk antibody into living cells has been found to induce a mitotic abnormality that contributes to the generation of aneuploidy, and this is an important finding in relation to tumour development. Indeed, previous studies have shown that the level of expression of a mitotic checkpoint gene, hsMAD2, is reduced and that another checkpoint gene, BUB1, is mutated in certain human cancer cells.

Cell Cycle Proteins↗
PubMed2000

Characterization of high-grade neuroendocrine tumors of the lung in relation to menin mutations.

It has been suggested that mutations in the menin gene play a role in the development of multiple endocrine neoplasia type 1 (MEN1)-associated and of sporadic forms of low- and intermediate-grade neuroendocrine tumors of the lung. In the present study, eight tumor specimens of large cell neuroendocrine carcinoma (LCNEC) and 13 of small cell lung cancer (SCLC), which represent a high-grade category of neuroendocrine tumors, were examined for the potential involvement of menin alterations as well as for the expression of various neuroendocrine markers and p53 and Rb abnormalities. All specimens expressed multiple neuroendocrine markers as expected and almost invariably carried p53 and Rb alterations. Unexpectedly, however, mutations in the menin gene were not detected in any of the high-grade neuroendocrine tumors examined. We thus conclude that menin mutations do not play a crucial role in the pathogenesis of high-grade subsets, in contrast to their suggested significant role in the development of low- and intermediate-grade subsets. Interestingly, loss of heterozygosity (LOH) in the menin gene appeared to be more prevalent in LCNEC (50%) than in SCLC (22%), suggesting a possible distinction between SCLC and LCNEC.

Carcinoma, Large Cell↗
PubMed2000

Bcl-2 inhibits calcineurin-mediated Fas ligand expression in antitumor drug-treated baby hamster kidney cells.

It is well known that human leukemia cells, such as HL-60 and U937 are sensitive to antitumor drugs, but human normal lung fibroblasts, such as WI-38 cells are resistant to the drugs. However, the mechanisms of the different responses to apoptosis in these cell lines remain unclear. We report here that an increase of Fas and Fas ligand (FasL) expression was required for antitumor drug-induced apoptosis in WI-38 and baby hamster kidney (BHK) cells, but not in HL-60 cells. Then, we used BHK cells transfected with the bcl-2 gene to investigate the involvement of complex formation of Bcl-2 and calcineurin. Calcineurin was imported to the nucleus in response to the drug treatment. Overexpression of Bcl-2 and cyclosporin A treatment inhibited the nuclear import and FasL expression, and as a result, both inhibited apoptosis. Although a caspase inhibitor, z-Asp-CH2-DCB, suppressed the drug-induced apoptosis, it failed to inhibit the drug-induced expression of Fas and FasL. These findings suggest that initially the Fas / FasL system is activated by calcineurin-dependent transcription followed by activation of the downstream caspase cascade resulting in antitumor drug-induced apoptosis in BHK cells, but not in HL-60 cells. Furthermore, Bcl-2 inhibits the nuclear import of calcineurin and suppresses calcineurin-mediated FasL expression during antitumor drug-induced apoptosis.

Animals↗
PubMed2000

Relationship between changes in volume of the oviductal fluid in the ampulla and the descent of ovulated eggs from the ampulla to the isthmus in mice.

Follicular growth and ovulation were induced in mice by administration of pregnant mare serum gonadotrophin (PMSG) followed 2 days later by human chorionic gonadotrophin; the day of PMSG injection was designated as day 0. The volume of the ampulla was measured and the location of the ovulated eggs determined at 06:00, 10:00, 14:00, 18:00 and 22:00 on day 3, and at 02:00 and 06:00 on day 4. The volume of the ampulla and hence oviductal fluid, peaked at 14:00 on day 3 and then declined. In all oviduct samples taken up to 14:00 on day 3, eggs were found exclusively in the ampulla. Thereafter, an increasing number of eggs were observed in the isthmus. Thus, the migration of eggs from the ampulla to the isthmus was concurrent with the decrease in oviductal fluid volume. The peak in the volume of oviductal fluid seen at day 3 is likely to coincide with the opening of the ampullary-isthmic junction of the oviduct.

Animals↗
PubMed2000

The yield of abnormal unfertilized eggs observed after repeated gonadotrophin-induced ovulation.

This study investigated whether or not the yield of abnormal eggs produced after repeatedly induced ovulation could be reduced by increasing the interval between gonadotrophin (GTH) administrations. Ovulation was induced, in a mouse model, by subcutaneous injection of pregnant mare serum GTH and human chorionic GTH given once (n = 10), twice (n = 10), three times (n = 10) or four times (n = 10) at intervals of 5 days. In 30 further mice, a fifth induction was performed either 5 (n = 10), 10 (n = 10) or 20 days (n = 10) following the fourth injection. Oviducts were examined microscopically, and the eggs were counted and examined for morphological abnormalities. In the mice who had received four GTH treatments, 33.3% (12 of 36) of the eggs were abnormal. After the fifth induced ovulation performed after an interval of 5, 10 or 20 days, the yield of abnormal eggs was 50.0% (five of 10), 23.1% (nine of 39) and 15.2% (seven of 46), respectively. These results indicate that prolongation of the interval between GTH administrations reduced the yield of abnormal eggs produced following repeatedly induced ovulation.

Animals↗
PubMed2000

Solitary fibrous tumor of the meninges in the posterior cranial fossa: magnetic resonance imaging and histological correlation--case report.

A 58-year-old female presented with a rare case of intracranial solitary fibrous tumor (SFT) manifesting as progressive ataxic gait and hearing loss on the left persisting for 6 months with recent symptoms of increased intracranial pressure. Computed tomography demonstrated a large isodense irregular-shaped mass in the left posterior cranial fossa. T2-weighted magnetic resonance imaging showed two components appearing as very low intensity and high intensity. Extreme-lateral suboccipital craniotomy was performed. Gross total resection was achieved except for some dural attachment in the jugular foramen. All symptoms and signs subsided after surgery. Histological, immunohistochemical, and electron microscopic examinations led to a diagnosis of SFT. The strongly hypointense areas on the T2-weighted images were hypocellular region characterized by disorganized spindle cells and thick bands of collagen. The hyperintense areas on the T2-weighted images were hypercellular region mimicking hemangiopericytoma. Strong immunoreactivity for CD34 was also helpful in the diagnosis. Electron microscopy revealed absence of pinocytic vesicles and dense laminae which are characteristic of hemangiopericytoma. The magnetic resonance imaging appearance of SFT seems to be pathognomonic.

Female↗