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Biomedical subjects

K Sakaguchi

Publications and source records attributed to K Sakaguchi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ectopic expression of BEAF32A in the Drosophila eye imaginal disc inhibits differentiation of photoreceptor cells and induces apoptosis.

Transgenic flies were established in which ectopic expression of boundary element-associated factor (BEAF) 32A was targeted to the Drosophila eye imaginal disc. The eyes of the adult fly displayed a severe rough eye phenotype. When these eyes were sectioned, most ommatidia were found to be fused and irregularly shaped rhabdomeres were observed. In the developing eye imaginal disc, expression of BEAF32A inhibited differentiation of photoreceptor cells. Expression of BEAF32A also induced extensive apoptosis of eye imaginal disc cells and, consistent with this, co-expression of baculovirus P35 in the eye imaginal disc suppressed the BEAF32A-induced rough eye phenotype. To investigate the effects of BEAF32A on regulation of chromatin structure, genetic crosses of the BEAF32A-overexpressing flies with loss-of-function mutants for genes encoding other boundary element-binding factors or regulators of chromatin structure were conducted. Interestingly, half-dose reduction of the su(Hw) gene strongly enhanced the rough eye phenotype induced by BEAF32A. Furthermore, genetic crosses of the transgenic flies with loss-of-function mutants for genes interacting with Polycomb revealed specific links between BEAF32A and genes such as Distalless and kohtalo, suggesting a relation to the chromatin insulator function of BEAF. In addition, genetic crosses of transgenic flies expressing BEAF32A with a collection of Drosophila deficiency stocks allowed us to identify several genomic regions, deletions of which caused enhancement or suppression of the BEAF32A-induced rough eye phenotype. The transgenic flies established in this study should be useful to identify targets of BEAF32A and its positive or negative regulators in Drosophila.

Animals↗
PubMed2001

Identification of a new point mutation in the human xanthine dehydrogenase gene responsible for a case of classical type I xanthinuria.

A 60-year-old Japanese man was diagnosed as having hypouricemia at an annual health check-up. The routine laboratory data was not remarkable except that the patient's hypouricemia and plasma levels of xanthine and hypoxanthine were much higher than those of normal subjects. Furthermore, the patient's daily urinary excretion of xanthine and hypoxanthine was markedly increased compared with reference values. The xanthine dehyrogenase activity of the duodenal mucosa was below the limits of detection. Nevertheless, allopurinol was metabolized to oxypurinol in vivo. Based on these findings, a subtype of classical xanthinuria (type I) was diagnosed. The xanthine dehyrogenase protein was detected by Western blotting analysis. Sequencing of the cDNA of the xanthine dehyrogenase obtained from the duodenal mucosa revealed that a point mutation of C to T had occurred in nucleotide 445. This changed codon 149 from CGC (Arg) to TGC (Cys), a finding that has not been previously reported in patients with classical xanthinuria type I.

Allopurinol↗
PubMed2001

Synthesis of sulfoquinovosylacylglycerols, inhibitors of eukaryotic DNA polymerase alpha and beta.

Sulfoquinovosyldiacylglycerols (SQDGs) and sulfoquinovosylmonoacylglycerols (SQMGs), bearing diverse fatty acids, were synthesized from D-glucose, and were examined for enzymatic inhibitions of DNA polymerase alpha and beta. These results indicated that the carbon numbers of the fatty acids were highly related to the activities, at least in vitro, of eukaryotic DNA polymerase inhibition.

Animals↗
PubMed2001

Cholecystokinin activation of 70-kDa S6 kinase in exocrine pancreas.

Cholecystokinin (CCK), a known mitogen for the exocrine pancreas, is shown to activate 70-kDa S6 kinase in isolated pancreatic acini. In this study, we examined the kinetics and cellular mechanisms of CCK-induced p70 S6 kinase activation in vivo and in vitro. Fasted mice were intraperitoneally injected with 0.01-10 microg/kg CCK analoge cerulein. Cerulein caused a concentration-dependent activation of p70 S6 kinase, with the maximal effect at 1-10 microg/kg. After 1 microg/kg cerulein administration, the kinase activity was increased at 5 min, peaked at 10 min, and subsequently decreased. Cerulein also caused a rapid and transient activation of Src. Prior administration of the tyrosine kinase inhibitor herbimycin A compeletely inhibited cerulein-induced Src activation, while the inhibition of p70 S6 kinase activity was partial. Similar results were obtained with pancreatic acinar cell line AR42J cells. These results suggest that tyrosine kinases, including Src as a possible candidate, are partly implicated in the signaling pathway of CCK-induced p70 S6 kinase activation in the exocrine pancreas.

Animals↗
PubMed2001

Over-expression of DREF in the Drosophila wing imaginal disc induces apoptosis and a notching wing phenotype.

BACKGROUND: DNA replication-related element binding factor (DREF) has been suggested to be involved in regulation of DNA replication- and proliferation-related genes in Drosophila. While the effects on the mutation in the DNA replication-related element (DRE) in cultured cells have been studied extensively, the consequences of elevating wild-type DREF activity in developing tissues have hitherto remained unclear. RESULTS: We over-expressed DREF in the wing imaginal disc using a GAL4-UAS targeted expression system in Drosophila. Over-expression of DREF induced a notching wing phenotype, which was associated with ectopic apoptosis. A half reduction of the reaper, head involution defective and grim gene dose suppressed this DREF-induced notching wing phenotype. Furthermore, this was also the case with co-expression of baculovirus P35, a caspase inhibitor. In addition, over-expression of the 32 kDa boundary element-associated factor (BEAF-32), thought to compete against DREF for common binding sites in genomic regions, rescued the DREF-induced notching wing phenotype, while a half reduction of the genomic region, including the BEAF-32 gene, exerted enhancing effects. To our knowledge, this is the first evidence for a genetic interaction between DREF and BEAF-32. CONCLUSION: The DREF-induced notching wing phenotype is caused by induction of apoptosis in the Drosophila wing imaginal disc.

Animals↗
PubMed2001

Spaciostructural analyses of mandibular and perioral soft tissue movements during mastication.

We considered that elucidation of the movements of perioral soft tissues during mastication would be useful in evaluating masticatory movements. However, evaluation of movements specific to soft tissues is difficult because movements of the surface of the lower face during mastication include movements of the muscles of facial expression and mandibular movements. The aims of this study were to elucidate the influence of mandibular movements on perioral soft tissue movements during mastication using principal component analysis (PCA) and to abstract the component of movement specific to soft tissues in order to evaluate masticatory movements from the movements of perioral soft tissues. The subjects were 10 healthy persons with complete natural dentition. The experimental food used in this study was sufficiently softened chewing gum. The results of this study showed that the movements of mandibular and perioral soft tissue were closely related in the first and third PCs; in other words, the second PC was the component of movement specific to soft tissues. Thus, elucidation of the second PC is useful for evaluation of masticatory movements from movements of perioral soft tissues.

Adult↗
PubMed2001

Characterization of plant proliferating cell nuclear antigen (PCNA) and flap endonuclease-1 (FEN-1), and their distribution in mitotic and meiotic cell cycles.

The biochemical and cell cycle-dependent properties of proliferating cell nuclear antigen (OsPCNA) and flap endonuclease-1 (OsFEN-1) were characterized from rice (Oryza sativa). OsPCNA was physically associated with OsFEN-1 and increased the flap-endonuclease activity of OsFEN-1 by 2.5-fold. Northern and Western blotting analysis revealed that OsPCNA and OsFEN-1 were present in meristematic tissues such as cultured cells, shoot apical meristem and root apical meristem. No expression was detected in the mature leaves, although they were exposed to UV. Both of these proteins were localized in the nuclei of the interphase cells including G1, S and G2, and in the nuclear region at telophase. The distribution patterns of plant PCNA and FEN-1 in meiotic cell progression were investigated using microsporocytes of lily (Lilium longiflorum cv. Hinomoto). During the leptotene to pachytene stages, PCNA and FEN-1 were localized in the nuclear region. The florescence gradually disappeared from diplotene to metaphase I. Interestingly, signals for PCNA formed 10-20 intense spots at leptotene. The number of spots decreased to 1-5 at zygotene and finally to 1 at pachytene. The roles of OsPCNA and OsFEN-1 in mitotic and meiotic cell cycles are discussed.

Antibodies↗
PubMed2001

Comparative study of sequential expression of the organizer-related genes in normal Cynops pyrrhogaster embryos and mesodermalized ectoderm.

An artificially mesodermalized ectoderm (mE) of early Cynops pyrrhogaster gastrula acquires the organizer property; the mE is able to induce the secondary axis. The expression of organizer-related genes was investigated during the mesodermalizing process of the mE. The expression of C. pyrrhogaster organizer-related genes, such as bra, gsc, lim-1, chd and noggin, were analyzed. Cynops pyrrhogaster shh expression was also investigated. The organizer-related genes were activated by 12 h after the mesoderm-inducing stimulus. It was noted that there was a temporal gap in the expression of each gene. The expression of bra and gsc seemed to be more quickly activated during the mesodermalizing process. While expression of lim-1 and noggin was activated later than that of bra and gsc, lim-1 expression was earlier than chd and noggin expression. Shh expression was activated later than lim-1/noggin. The present study suggests the possibility that the bra/gsc, lim-1, chd, noggin and shh genes are expressed one by one in that order during the mesodermalizing of the presumptive ectoderm. It also indicates that the sequence is not always consistent with that of the whole embryo during normal embryogenesis. The meaning of the discrepancy will be discussed in connection with the cascade of certain genes expressed during the mesodermalizing process.

Actins↗
PubMed2001

Modulation of doxorubicin sensitivity by cyclosporine A in hepatocellular carcinoma cells and their doxorubicin-resistant sublines.

BACKGROUND AND AIMS: Cyclosporine A (Cys) and verapamil (Ver) sensitize multidrug-resistant (MDR) cells to various anticancer drugs by interacting with membrane glycoproteins involved in the drug efflux. In the present study, we assessed the effect of Cys on the modulation of doxorubicin (DOR) sensitivity in hepatocellular carcinoma (HCC) cell lines, and their DOR-resistant sublines. METHODS: The sensitivity to DOR and the chemosensitizing effects of Cys were assessed by using two human HCC cell lines, PLC/PRF/5 and Hep-3B, and their DOR-resistant sublines, PLC/DOR and 3B/DOR. The expression of multidrug resistance 1 (MDR1) and multidrug resistance-associated protein (MRP) mRNA in these cells were detected by using a RT-PCR. The HCC cell lines grown in individual wells of 24-well plates were incubated with DOR that were sequentially diluted in culture medium in combination with 5 micromol/L Cys for 24 h. The cell viability in each well was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: The mRNA of MDR1 and that of MRP were readily detectable in the HCC cell lines by RT-PCR. When 5 micromol/L Cys was added to the culture, the 50% inhibiting concentration (IC50) of DOR was reduced from 0.93 +/- 0.29 microg/mL to 0.32 +/- 0.10 microg/mL in PLC/PRF/5, and from 0.25 +/- 0.07 microg/mL to 0.09 +/- 0.04 microg/mL in Hep-3B. Furthermore, in the presence of 5 micromol/L Cys, the IC50 of DOR was reduced from 48.63 +/- 17.04 microg/mL to 0.49 +/- 0.14 microg/mL in PLC/DOR, and from 4.60 +/- 1.22 microg/mL to 0.15 +/- 0.06 microg/mL in 3B/DOR. The amounts of PCR products of MDR1 mRNA in PLC/DOR and 3B/DOR were greater than those in PLC/PRF/5 and Hep-3B, respectively. CONCLUSIONS: In HCC, the amplification of MDR1 mRNA is probably the main mechanism underlying acquired DOR resistance. Cyclosporine is also indicated to be highly active in potentiating the anticancer activity of DOR in HCC cells and their DOR-resistant sublines.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Three-dimensional structural model analysis of the binding site of lithocholic acid, an inhibitor of DNA polymerase beta and DNA topoisomerase II.

The molecular action of lithocholic acid (LCA), a selective inhibitor of mammalian DNA polymerase beta (pol beta), was investigated. We found that LCA could also strongly inhibit the activity of human DNA topoisomerase II (topo II). No other DNA metabolic enzymes tested were affected by LCA. Therefore, LCA should be classified as an inhibitor of both pol beta and topo II. Here, we report the molecular interaction of LCA with pol beta and topo II. By three-dimensional structural model analysis and by comparison with the spatial positioning of specific amino acids binding to LCA on pol beta (Lys60, Leu77, and Thr79), we obtained supplementary information that allowed us to build a structural model of topo II. Modeling analysis revealed that the LCA-interaction interface in both enzymes has a pocket comprised of three amino acids in common, which binds to the LCA molecule. In topo II, the three amino acid residues were Lys720, Leu760, and Thr791. These results suggested that the LCA binding domains of pol beta and topo II are three-dimensionally very similar.

African Swine Fever Virus↗
PubMed2001

Treatment of severe hypothyroidism reduced serum creatinine levels in two chronic renal failure patients.

Short-term hypothyroidism has been associated with a reversible rise in serum creatinine levels in patients with normal renal function. A remarkable decline in serum creatinine levels associated with a treatment of severe and prolonged hypothyroidism has rarely been reported so far. We present here 2 patients with chronic renal failure in whom treatment for hypothyroidism resulted in a significant and sustained reduction of their serum creatinine levels. These cases indicate that because hypothyroidism may aggravate the serum creatinine levels, TSH should be considered in screening procedures of patients with chronic renal failure presenting with recent accelerated aggravation of renal function. Hypothyroidism per se, one of its complications or one of its associated autoimmune diseases might play a role in modifying the underlying renal problem.

Adult↗
PubMed2001

A natural history of adrenocorticotropin-independent bilateral adrenal macronodular hyperplasia (AIMAH) from preclinical to clinically overt Cushing's syndrome.

A 49-year-old man was referred to our hospital for the treatment of gallstones in 1993. Bilateral adrenal nodular masses were detected incidentally by abdominal computed tomography. He had no clinical signs of Cushing's syndrome such as central obesity, striae of skin and diabetes mellitus. We performed cholecystectomy and partial adrenalectomy of right adrenal gland as a biopsy, and diagnosed him as preclinical Cushing's syndrome due to adrenocorticotropin-independent bilateral adrenal macronodular hyperplasia (AIMAH) based on endocrinological and histological examinations. We followed him up for 7 years. During the observation period, the sizes of both adrenal glands increased gradually, and finally serum cortisol level increased beyond normal range, and he showed a Cushingoid appearance such as moon face and central obesity. His skin became atrophic and very fragile, and the bone mineral density of his lumbar spine was extremely low. Serum cortisol level was elevated, and plasma ACTH level was always suppressed. Urinary excretion of 17-hydroxycorticosteroid and free cortisol were increased. Diurnal rhythm of cortisol and ACTH was completely lost and high dose (8 mg/day) dexamethasone did not suppress urinary 17-hydroxycorticosteroid excretion. He became clinically overt Cushing's syndrome. We recommended total adrenalectomy, but he refused it. It is important to know the natural history of preclinical Cushing's syndrome due to AIMAH when choosing an adequate treatment.

17-Hydroxycorticosteroids↗
PubMed2001

Therapeutic effects of azathioprine in combination with low-dose prednisolone in patients with intractable autoimmune hepatitis type 1.

This study evaluated the effects of azathioprine in combination with low-dose prednisolone in the management of patients with intractable autoimmune hepatitis. Thirteen patients with intractable autoimmune hepatitis who had an incomplete or arrested response to conventional prednisolone therapy, or who relapsed during prednisolone maintenance therapy were additionally administered 50 or 100 mg/day of azathioprine in combination with prednisolone. This regimen reliably induced complete remission in 12 of 13 patients, and these 12 remained in remission during the follow-up period with maintenance therapy of 50 mg/day of azathioprine in combination with 5 mg/day of prednisolone. The findings of the current study indicate that the azathioprine and low-dose prednisolone combined therapy may offer a satisfactory alternative therapy for patients with intractable autoimmune hepatitis who have an incomplete or arrested response to conventional prednisolone therapy, or who relapse during prednisolone maintenance therapy.

Adult↗
PubMed2001

[A case of inflammatory myopathy worsened by miscarriage with autoimmune disorder-associated disease].

The patient was 42-year-old woman who had exhibited elevated levels of serum creatine kinase(CK) and intermittent weakness of proximal muscles since her thirties. She had a history of palmoplantar pustulosis, Mondor's disease and recurrent miscarriages. Basedow's disease, which had been treated with antithyroid drugs since 37 years of age, recurred during the fourth pregnancy. After the pregnancy was terminated in the sixth week, weakness and grasp pain in the proximal muscles developed. The biopsy of biceps brachii muscle showed necrosis and reconstruction of muscle fibers with equivocal inflammatory cells, which was compatible with the findings for inflammatory myopathy such as polymyositis(PM). She was treated with prednisolone and the weakness and grasp pain in the proximal muscles were resolved. PM beginning during a woman's reproductive period is rare, and few studies have examined the association between PM and pregnancy. In this case, pregnancy and her past diseases were considered to be linked to an autoimmune abnormality that might have contributed to the inflammatory myopathy.

Abortion, Habitual↗