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Y Saka

Publications and source records attributed to Y Saka.

At least 19 recordsLinked to original sources
PubMed2003

[Complete disruption of cervical trachea, whose distal airways were migrated into the mediastinum].

The first case was a 55-year-old man, who suffered by a rope while driving his motor bicycle. On 7th day after injury, tracheotomy was scheduled due to progressive dyspnea. Following intubation of a endotracheal tube, his trachea was ruptured. The second case was a 16-year-old man, who was stabbed his trachea with a sword by his mother. His trachea completely separated following coughing during the examination of bronchoscopy. For 2 cases, we immediately excised their necks for tracheotomy but couldn't find their distal portion of trachea, because they were migrated into the mediastinum. We inserted our finger into the mediastinum for exploration and could draw it back. Both case's postoperative course was uneventful. Whenever cervical trachea is completely separated, tracheal distal end may be pulled down into the mediastinum. We invited new technique of exploration for migrated trachea using our finger.

Adolescent↗
PubMed2001

Spatial and temporal patterns of cell division during early Xenopus embryogenesis.

We describe the spatial and temporal patterns of cell division in the early Xenopus embryo, concentrating on the period between the midblastula transition and the early tailbud stage. Mitotic cells were identified using an antibody recognising phosphorylated histone H3. At least four observations are of interest. First, axial mesodermal cells, including prospective notochord, stop dividing after involution and may not divide thereafter. Second, cell division is more pronounced in the neural plate than in nonneural ectoderm, and the pattern of cell division becomes further refined as neurogenesis proceeds. Third, cells in the cement gland cease proliferation completely as they begin to accumulate pigment. Finally, the precursors of peripheral sensory organs such as the ear and olfactory placode undergo active cell proliferation when they arise from the sensorial layer of the ectoderm. These observations and others should provide a platform to study the relationship between the regulation of developmental processes and the cell cycle during Xenopus embryogenesis.

Animals↗
PubMed2000

Xwnt11 and the regulation of gastrulation in Xenopus.

The molecular basis of gastrulation is poorly understood. In this paper we address this problem by taking advantage of the observation that the transcription activator Brachyury is essential for gastrulation movements in Xenopus and mouse embryos. We infer from this observation that amongst the target genes of Brachyury are some that are involved in the regulation of gastrulation. In the course of a screen for Brachyury targets we identified Xwnt11. Use of a dominant-negative Xwntll construct confirms that signalling by this class of Wnts is essential for normal gastrulation movements, and further investigation suggests that Xwntll signals not through the canonical Wnt signalling pathway involving GSK-3 and beta-catenin but through another route, which may require small GTPases such as Rho and Rac. Future work will concentrate on elucidating the Xwnt11 signal transduction pathway and on investigating its influence on cell shape and polarity during Xenopus gastrulation.

Animals↗
PubMed2000

A screen for targets of the Xenopus T-box gene Xbra.

Brachyury (T), a member of the T-box gene family, is essential for the formation of posterior mesoderm and notochord in vertebrate development. Expression of the Xenopus homologue of Brachyury, Xbra, causes ectopic ventral and lateral mesoderm formation in animal cap explants and co-expression of Xbra with Pintallavis, a forkhead/HNF3beta-related transcription factor, induces notochord. Although eFGF and the Bix genes are thought to be direct targets of Xbra, no other target genes have been identified. Here, we describe the use of hormone-inducible versions of Xbra and Pintallavis to construct cDNA libraries enriched for targets of these transcription factors. Five putative targets were isolated: Xwnt11, the homeobox gene Bix1, the zinc-finger transcription factor Xegr-1, a putative homologue of the antiproliferative gene BTG1 called Xbtg1, and BIG3/1A11, a gene of unknown function. Expression of Xegr-1 and Xbtg1 is controlled by Pintallavis alone as well as by a combination of Xbra and Pintallavis. Overexpression of Xbtg1 perturbed gastrulation and caused defects in posterior tissues and in notochord and muscle formation, a phenotype reminiscent of that observed with a dominant-negative version of Pintallavis called Pintallavis-En(R). The Brachyury-inducible genes we have isolated shed light on the mechanism of Brachyury function during mesoderm formation. Specification of mesodermal cells is regulated by targets including Bix1-4 and eFGF, while gastrulation movements and perhaps cell division are regulated by Xwnt11 and Xbtg1.

Amino Acid Sequence↗
PubMed1998

Interaction of amphotericin B with cholesterol in monolayers, aqueous solutions, and phospholipid bilayers.

The interaction of amphotericin B (AmB) with cholesterol was investigated in monolayers, aqueous solutions, and phospholipid vesicles. When AmB was mixed with cholesterol, it formed a stable monolayer, implying complex formation in which the stoichiometry was primarily 1:1 AmB:cholesterol. However, the interaction of AmB with cholesterol in aqueous solutions and lipid vesicles was more complex. In aqueous solutions, cholesterol at low concentrations increased the aggregation of AmB. But higher concentrations of cholesterol caused dissociation of the aggregates of AmB due to the formation of AmB-cholesterol complexes. In lipid vesicles, the effect of cholesterol was different from that in aqueous solutions. Both in aqueous solutions and lipid vesicles, the overall dissociation of AmB molecules occurred on interaction with cholesterol. In addition, the interaction of lipid membranes with AmB-cholesterol complexes was investigated by differential scanning calorimetry. The incorporation of AmB into lipid bilayers led to broadening of the lipid transition and a slight decrease in the transition enthalpy, showing that one lipid molecule per AmB molecule was immobilized. However, the number of immobilized lipid molecule per AmB molecule increased in the coexistence of cholesterol, due to the complex formation between AmB and cholesterol.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Damage and replication checkpoint control in fission yeast is ensured by interactions of Crb2, a protein with BRCT motif, with Cut5 and Chk1.

Fission yeast Cut5/Rad4 plays a unique role in the genome maintenance as it is required for replication, replication checkpoint, and normal UV sensitivity. It is unknown, however, how Cut5 protein is linked to other checkpoint proteins, and what part it plays in replication and UV sensitivity. Here we report that Cut5 interacts with a novel checkpoint protein Crb2 and that this interaction is needed for normal genome maintenance. The carboxyl terminus of Crb2 resembles yeast Rad9 and human 53BP1 and BRCA1. Crb2 is required for checkpoint arrests induced by irradiation and polymerase mutations, but not for those induced by inhibited nucleotide supply. Upon UV damage, Crb2 is transiently modified, probably phosphorylated, with a similar timing of phosphorylation in Chk1 kinase, which is reported to restrain Cdc2 activation. Crb2 modification requires other damage-sensing checkpoint proteins but not Chk1, suggesting that Crb2 acts at the upstream of Chk1. The modified Crb2 exists as a slowly sedimenting form, whereas Crb2 in undamaged cells is in a rapidly sedimenting structure. Cut5 and Crb2 interact with Chk1 in a two-hybrid system. Moreover, moderate overexpression of Chk1 suppresses the phenotypes of cut5 and crb2 mutants. Cut5, Crb2, and Chk1 thus may form a checkpoint sensor-transmitter pathway to arrest the cell cycle.

Amino Acid Sequence↗
PubMed1995

A novel essential fission yeast gene pad1+ positively regulates pap1(+)-dependent transcription and is implicated in the maintenance of chromosome structure.

Fission yeast pap1+ gene encodes an AP-1-like transcription factor, whose overexpression can confer resistance to staurosporine, a protein kinase inhibitor. We have previously identified a target gene (p25) for pap1+, and shown that, crm1+, which is required for maintenance of higher order chromosome structure, negatively regulates pap1-dependent transcription. In this study, we have characterized a novel gene, pad1+, which was isolated as a multicopy plasmid capable of conferring staurosporine-resistance. We showed that high copy pad1+ induces transcriptional activation of the p25 gene and that the induction by pad1+ is dependent on the pap1+ gene. Furthermore, a cis-element analysis of the 5'-region of the p25 gene showed that two elements (an AP-1 site and a 14 bp palindrome sequence) where pap1 binds in vitro is essential for the induction by pad1+. These results indicate that pad1 can positively regulate pap1-dependent transcription. Through an electromobility shift assay we showed that overexpression of pad1+ is not capable of enhancing the DNA-binding activity of pap1 directly. The pad1+ gene encodes a 35 kDa protein that has significant identity (68%) to Caenorhabditis elegans F37A4.5, and is also similar to mouse Mov34 and human C6.1A. Gene disruption experiments have demonstrated that pad1+ is essential for viability. A disruption mutant of pad1+ obtained after spore germination exhibited an elongated cell body with abberantly folded chromosomes. A mitotic plasmid loss experiment also produced similar cells having an abnormal chromosome structure. These suggest that pad1+ may play an important role in higher order chromosome structure. Taken concurrently with our previous results, two essential genes pad1+ and crm1+ regulate pap1-dependent transcription; pad1+ and crm1+ are positive and negative regulators, respectively.

Amino Acid Sequence↗
PubMed1995

[Studies on colonic mucus release--II. Damaged colon mucosa].

The release of goblet cell mucus (GCM) was examined in immune reaction-system of colonic mucosa of rats (SD rats). We previously reported that in the immune reaction of normal colon of rats, the discharge of colonic GCM was not increased by intrarectal instillation (challenge) of several test-antigens after repeated immunization of single BSA antigen through rectal mucosa, and there was difference in local antigen-antibody reaction on the surface of normal mucosa between small intestine and colon. In the present study we investigated the release of colonic GCM in local antigen-antibody system in rats of damaged colon mucosa, who had repeated immunization of BSA after damage induction by intracolonic infusion of formalin. Consequently, the discharge of colonic GCM increased associated with local antigen-antibody reaction in animals after damage induction by formalin. It is suggested that when the mucosal barrier is disrupted, enhanced release of colonic GCM is occurred by the local immune reaction on the surface of colonic mucosa.

Animals↗
PubMed1994

Fission yeast cut5 links nuclear chromatin and M phase regulator in the replication checkpoint control.

Fission yeast temperature-sensitive cut5 (cell untimely torn) mutants are defective in initiation and/or elongation of DNA replication but allow mitosis and cell division at a restrictive temperature. We show that the cut5 protein (identical to rad4) (i) is an essential component of the replication checkpoint system but not the DNA damage checkpoint, and (ii) negatively regulates the activation of M phase kinase at mitotic entry. Even if the replication checkpoint has been activated previously, cut5 mutations allow mitosis and cell division after shift to 36 degrees C. Transcription of cut5+ is not under the control of the START gene cdc10+. The cut5 protein is enriched in the nucleus, consisting of repeating domains. An essential domain which resembles the proto-oncoprotein Ect2 has a strong negative effect on the entry into mitosis when overexpressed. Expression of the cut5 mutant phenotype requires the function of the M phase regulator genes cdc2+, cdc25+ and cdc13+. The cut5 protein forms a novel, essential link between DNA synthesis and M phase activation in the replication checkpoint control pathway.

Amino Acid Sequence↗
PubMed1994

Fission yeast cut3 and cut14, members of a ubiquitous protein family, are required for chromosome condensation and segregation in mitosis.

Fission yeast temperature-sensitive mutants cut3-477 and cut14-208 fail to condense chromosomes but small portions of the chromosomes can separate along the spindle during mitosis, producing phi-shaped chromosomes. Septation and cell division occur in the absence of normal nuclear division, causing the cut phenotype. Fluorescence in situ hybridization demonstrated that the contraction of the chromosome arm during mitosis was defective. Mutant chromosomes are apparently not rigid enough to be transported poleward by the spindle. Loss of the cut3 protein by gene disruption fails to maintain the nuclear chromatin architecture even in interphase. Both cut3 and cut14 proteins contain a putative nucleoside triphosphate (NTP)-binding domain and belong to the same ubiquitous protein family which includes the budding yeast Smc1 protein. The cut3 mutant was suppressed by an increase in the cut14+ gene dosage. The cut3 protein, having the highest similarity to the mouse protein, is localized in the nucleus throughout the cell cycle. Plasmids carrying the DNA topoisomerase I gene partly suppressed the temperature sensitive phenotype of cut3-477, suggesting that the cut3 protein might be involved in chromosome DNA topology.

Amino Acid Sequence↗
PubMed1994

Coupling of DNA replication and mitosis by fission yeast rad4/cut5.

The fission yeast cut5+ (identical to rad4+) gene is essential for S phase. Its temperature-sensitive (ts) mutation causes mitosis while S phase is inhibited: dependence of mitosis upon the completion of S phase is abolished. If DNA is damaged in mutant cells, however, cell division is arrested. Thus the checkpoint control system for DNA damage is functional, while that for DNA synthesis inhibition is not in the cut5 mutants. Transcription of the cut5+ gene is not under the direct control of cdc10+, which encodes a transcription factor for the START of cell cycle. The transcript level does not change during the cell cycle. The protein product has four distinct domains and is enriched in the nucleus. Its level does not alter during the cell cycle. The N-domain is important for cut5 protein function: it is essential for complementation of ts cut5 mutations and its overexpression blocks cell division. Furthermore, it resembles the N-terminal repeat domain of proto-oncoprotein Ect2, which, in the C-domain, contains a regulator-like sequence for small G proteins. We discuss a hypothesis that the cut5 protein is an essential component of the checkpoint control system for the completion of DNA synthesis. The restraint of mitosis until the completion of S phase is mediated by the cut5 protein, which can sense the state of chromosome duplication and negatively interacts with M phase regulators such as cdc25 and cdc2.

Cell Cycle↗
PubMed1994

[Effects of volatile anesthetics on force interval relationships in guinea-pig atrial preparations].

Depressant effects of halothane, enflurane and isoflurane on isolated guinea-pig left atrial muscles bathed in Tyrode's solution at 30 degrees C were examined. Contractions were elicited by stimulation through external field electrodes while tension was recorded continuously. Frequency-force relationships at stimulation rates of 0.1, 0.2, 0.5 and 1 Hz were studied. The pD2 values of these volatile anesthetics at each stimulation rates were not different significantly, suggesting the frequency-independent depressions of these anesthetics. Interval-strength relationships at time intervals of 0.3-20 sec during 1 Hz-stimulation were also studied. Mechanical restitution curves after converting to logistic function reached a peak at 8-20 sec and were fitted well to double exponential functions with time constants of 200-600 msec (k1) and 2-6 sec (k2). All volatile anesthetics depressed the magnitude constants for fast response in a dose dependent manner. Accordingly, at high concentrations, mechanical resuscitation curves tended to fit single exponential function. Halothane and enflurane did not alter time constant k1, k2 significantly, while isoflurane increased k2 significantly. These results suggest that the mechanisms of myocardial depressant effects are different between these anesthetics.

Anesthetics, Inhalation↗
PubMed1994

[Aggressive transformation of an indolent myeloma with abdominal extramedullary plasmacytoma after 6-year period of observation].

62-year-old female, who had been under observation for an indolent myeloma for six years without therapy, was admitted because of left flank pain. Various imaging modalities disclosed left pleural effusion, and a huge abdominal tumor involving the left crus of the diaphragm, spleen, stomach, pancreatic tail, left adrenal gland, left kidney and left posterior abdominal wall. Morphological and immunological examinations revealed extensive proliferation of more anaplastic myeloma cells within the tumor and in the pleural effusion than those in bone marrow on admission or at the beginning of the period of observation. Chemotherapy reduced serum M-protein, but LDH, the volume of the pleural effusion, and the size of the tumor increased. She died of pancreatitis associated with massive bleeding from the gastric tumor. Renal function was well preserved until her terminal phase. The clinical course showed the progression of indolent myeloma into an aggressive one without chemotherapeutic intervention, implying a rare subtype in terms of the natural history of multiple myeloma.

Abdominal Neoplasms↗