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A Koga

Publications and source records attributed to A Koga.

At least 19 recordsLinked to original sources
PubMed1999

Homogeneity in the structure of the medaka fish transposable element Tol2.

The hAT family is a group of transposable elements of the terminal inverted repeat class, which includes Ac of maize, hobo of Drosophila and Tam3 of Antirrhinum (snapdragon). All the members of this family so far examined are known to comprise complete and defective copies, with a good correspondence to autonomous and non-autonomous elements, respectively. Internal deletion is the most common cause of defective copies. Tol2, a transposable element of the medaka fish Oryzias latipes, is a member of the hAT family. We examined, mainly by the genomic Southern blot analysis, variation in the structure of copies of this element, and revealed that there are few or no internally deleted copies. This situation is unusual in a member of the hAT family. Possible causes of this anomaly are discussed.

Animals↗
PubMed1998

Excision of the tol2 transposable element of the medaka fish, Oryzias latipes, in zebrafish, Danio rerio.

The Tol2 element is a transposable element in Oryzias latipes (the medaka fish) found in the tyrosinase gene locus of the tyrosinase-deficient mutant medaka fish and has been shown to be excised from the genome during medaka embryogenesis (Koga, A., Suzuki, M., Inagaki, H., Bessho, Y., Hori, H., 1996. Transposon element in fish. Nature 383, 30). It is, however, not known whether the Tol2 element is an autonomous element. To determine whether the cloned Tol2 element is an autonomous element and whether excision can occur also in the other fish species, the plasmid DNA harboring the Tol2 element was injected to fertilized eggs of zebrafish, Danio rerio, and the total DNA extracted from the embryos 9-10h after the injection was analyzed by PCR. When a plasmid with the full-length Tol2 element was used for the microinjection, in 39 out of 43 injected embryos, we found generation of short PCR products indicative of the loss of the Tol2 element from the injected plasmid. Ten of these cases were analyzed at the DNA sequence level, and nine of them showed either precise excision of the Tol2 element (three cases) or nearly precise excision of the element with the addition of a few nucleotides of the target duplication (six cases). When a deletion version of the Tol2 element that retained the terminal inverted repeats but lacked about one-fourth of the open reading frame-coding region was used for the microinjection, such short PCR products could not be amplified from any of the injected embryos (0 out of 30). Thus, the Tol2 element is capable of excision in zebrafish embryos, presumably dependent on a putative transposase encoded by the Tol2 element itself. This transient embryonic excision assay using zebrafish should be useful to analyze the structure and the function of the transposase and cis-elements necessary for excision. Also, this study implies the potential use of the Tol2 element in transgenesis and insertional mutagenesis in both zebrafish and the medaka fish.

Animals↗
PubMed1998

The tyrosinase gene from medakafish: transgenic expression rescues albino mutation.

We have determined the 9.8 kb genomic nucleotide sequence of the tyrosinase gene and its 5 upstream region from a teleost, medakafish (Oryzias latipes), and shown that the coding region is composed of five exons and four introns, spanning 4.7 kb. While the number and sizes of the exons were found to be similar to those of mammalian tyrosinase genes, however, the total size of the coding region (4.7 kb) was demonstrated to be less than one tenth those of mouse (ca. 70 kb) and human (> 70 kb) genes. Primer extension analysis revealed that the transcription initiation site starts with a long untranslated leader sequence (340 nucleotide long) from the AUG start codon. A characteristic CATGTG sequence known as a putative regulatory motif in melanocyte-specific genes was present in the 131st base upstream from the initiation site, while other typical regulatory elements such as the TATA-box or M-box common to terrestrial vertebrates were lacking. Transgenic experiments were carried out by microinjecting two kinds of plasmid clones into fertilized eggs of the albino i(l) mutant: one consisting of the genomic tyrosinase gene with the 10 kb 5 upstream region and the other the tyrosinase cDNA with the 3 kb 5 upstream region. The results showed that 53 and 45 of 114 and 118 transgenic eggs, respectively, developed normally beyond hatching and 15 and 10 exhibited a mosaic pattern of pigmentation. Despite the absence of typical regulatory elements like a TATA-box in both cases correct melanin pigmentation was obtained without ectopic expression. Thus, transgenic expression rescued from the albino-i(l) mutation, and the i locus of the medaka genome can be concluded to encode the tyrosinase gene.

Albinism↗
PubMed1998

An active Ac-like transposable element in teleost fish.

The i4/i4 genotype of the medakafish, Oryzias latipes, exhibits a quasi albino phenotype due to insertion of a novel transposable element, Tol2, into the tyrosinase gene. Tol2 is 4681 bp in length, has short inverted terminal repeats, and contains four ORFs with the potential to encode a transposase protein. Excision activity of the element has been detected by PCR analysis. Genomic Southern of the Tol2 element revealed that about 20 copies are present in the diploid genome. Dot-matrix comparisons of amino acid sequences of ORFs show relatively high similarity with transposases from Ac of maize, hobo of Drosophila, and Tam3 of snapdragon, which are all active transposable elements. Tol2 is thus concluded to be an active Ac-like transposable element probably encoding a transposase protein. It should therefore find application as a unique material for establishing a gene tagging system in fish.

Journal Article↗
PubMed1997

Fine structure of cholesterolosis in the human gallbladder and the mechanism of lipid accumulation.

Gallbladders with cholesterolosis removed surgically for cholelithiasis were studied by light and electron microscopy as well as by cytochemical methods to demonstrate the presence of free cholesterol in the epithelial cells. Lipid droplets were found not only in the submucosa, but also in the infranuclear cytoplasm of epithelial cells. These contained well developed mitochondria and an agranular endoplasmic reticulum. Macrophages were often present between the epithelial cells and the submucosa, and protruded numerous processes, which also contained well developed cell organelles, abundant lysosomes and lipid droplets. With the excessive lipid deposition, macrophages were filled with lipid droplets and became foam cells. In the epithelial cells, many reaction precipitates occurred after digitonin treatment and some of them were observed in the endoplasmic reticulum. It is suggested, therefore, that free cholesterol is absorbed by epithelial cells and thereafter becomes esterified in the endoplasmic reticulum and thus appears as lipid droplets. Lipid droplets synthesized in the epithelial cells may then be released into the intercellular space, and phagocytosed there by macrophages. It is thus suggested that macrophages filled with lipid droplets may become too large and rigid to pass through the endothelium of lymph vessels, and those large "foam cells" may cause the destruction of lymph vessels. Those sequential events should eventually advance the accumulation of foam cells in the submucosa.

Cholelithiasis↗
PubMed1997

Molecular cloning of a rat 49-kDa TBP-interacting protein (TIP49) that is highly homologous to the bacterial RuvB.

TBP as a central component in transcriptional regulation can form complexes with various regulatory factors. Using histidine-tagged TBP for affinity-purification of TBP-bound proteins, we isolated a 49-kD protein termed TBP-interacting protein 49 (TIP49) from rat liver nuclear extracts. We cloned the entire cDNA of TIP49 encoding a novel polypeptide of 456 amino acids, and thereafter established an FM3A cell line that constitutively expressed an epitope-tagged TBP. Immunoprecipitation analysis of the cell extracts indicated that TIP49 and TBP were present in an identical complex. Interestingly, the amino acid sequence of TIP49 exhibited high similarity to those sequences of the RuvB bacterial recombination factors which direct branch migration of the Holliday junction and contain the Walker A and B motifs responsible for ATP binding and ATP hydrolysis. These findings suggest that TIP49 is a putative ATP-dependent DNA helicase.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1997

Albinism due to transposable element insertion in fish.

The i locus of the medaka fish, Oryzias latipes, is responsible for tyrosinase expression, and several mutant alleles have been identified. The genotype i1/i1 exhibits a complete albino phenotype, having pale orange-red skin and red eyes. This mutant lacks in vivo tyrosinase activity. The genotype i4/i4, on the other hand, shows a quasi-albino phenotype with skin as bright as that of i1/i1 but with red-wine-colored eyes. At the light microscope level, reduced pigmentation is observed both in the skin and eyes of this mutant. The tyrosinase genes for the i1 and the i4 alleles were cloned and sequenced, and compared with that of the wild-type tyrosinase gene. The i1 allele was found to contain a 1.9-kb transposable element in the 1st exon, and the i4 allele was found to contain a 4.7-kb transposable element in the 5th exon. Both i1 and i4 are alleles that were found in a commercial breeding population. The insertion of a transposable element thus appears to constitute a natural cause of mutations that cause albinism in this organism.

Albinism↗
PubMed1997

[Continuous arterial infusion of low-dose cisplatin, 5-fluorouracil as adjuvant therapy in cytoreductive surgery for advanced hepatocellular carcinoma].

We investigated the effectiveness of continuous arterial infusion of low-dose CDDP, 5-FU for residual cancer after cytoreductive surgery for advanced hepatocellular carcinoma. Thirty-one patients with unresectable advanced hepatocellular carcinoma were classified into two groups by adjuvant therapy after reduction surgery: 1) Low-dose FP Group: 17 patients; continuous arterial infusion of low-dose CDDP, 5-FU via implanted port system; 2) Conventional group: 8 patients; Lipiodolization (6 cases) and transcatheter arterial embolization (2 cases). The five-year survival rate in the low-dose FP group was 34.8%, the efficacy was 64.7%, CR: 6 (35.3%); PR: 5; NC: 4; PD: 2. Thus, continuous arterial infusion of low-dose CDDP, 5-FU was effective as adjuvant therapy in cytoreductive surgery for advanced hepatocellular carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Recurrent exercise-induced acute renal failure in renal hypouricemia.

We describe a male patient with four episodes of acute renal failure after strenuous exercise occurring between the age of 14 and 25 years. He was found to have low serum uric acid (0.4 mg dl-1 after recovery) and high fractional excretion of uric acid. A benzbromarone/pyrazinamide test suggested that renal hypouricemia was due to defective proximal tubular reabsorption of uric acid at a presecretory site. A renal biopsy revealed acute tubular necrosis, a renal computer tomography scan showed patchy contrast enhancement and a treadmill exercise test induced an immediate fall in creatinine clearance. These findings suggest that the cause of acute renal failure was renal vasoconstriction rather than obstruction by uric acid crystals.

Acute Kidney Injury↗
PubMed1996

[Usefulness of continuous arterial infusion chemotherapy for post operative multiple recurrence and residual hepatocellular carcinoma].

Twenty five patients with postoperative multiple recurrence and residual hepatocellular carcinoma received continuous arterial infusion of CDDP and 5-FU via implanted reservoir. For the next five days, 10 mg/body of CDDP and 250 mg/body of 5-FU using arterial infusion were administered. It was discontinued for two days as one course, and 4 courses were basally administered. The efficacy rate was 60%, and there were 7 (28%) CR (complete response) cases. The survival rate was 76.0% for 1 year and 36.5% for 3 years, which is a favorable result considering their advanced stage. Thus, this treatment seemed to be effective for multiple hepatocellular carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Insertion of a novel transposable element in the tyrosinase gene is responsible for an albino mutation in the medaka fish, Oryzias latipes.

In the medaka fish (Oryzias latipes) many mutants for body color have been isolated. A typical example is the recessive oculocutaneous albino mutant i, which has amelanotic skin and red-colored eyes with no tyrosinase activity. To cast light on the molecular basis of the albino mechanism, we performed Southern blot analysis of genomic DNA from the mutant with an authentic tyrosinase gene probe; the results demonstrate that an extra 1.9 kb fragment is present inside the first exon. The insertion is responsible for the oculocutaneous albinism. About 80 copies of this fragment are present in the genomes of albino-i and wild-type fish; these repeated sequences are here designated Tol1 elements and the particular element found in the tyrosinase gene of albino-i is denoted Tol1-tyr. The nucleotide sequence of Tol1-tyr shows that the fragment (i) carries terminal inverted repeats of 14 bp, and (ii) is flanked by duplicated 8 bp segments of the host chromosome. These are properties of DNA-mediated transposable elements. Comparison of the nucleotide sequence of Tol1-tyr with other sequences in DNA databases, with special attention to sequences of transposable elements known to date, did not reveal any similarity. Thus, Tol1 constitutes a hitherto unknown family of DNA transposable elements.

Albinism↗
PubMed1995

[The study of continuous arterial infusion chemotherapy with CDDP and 5-FU in patients with hepatocellular carcinoma].

Between Feb. 1992 and April in 1995, 22 patients with hepatocellular carcinoma (10, recurrence; 12, unresectable) received continuous arterial infusion of CDDP and 5-FU via implanted reservoir. For the next five days, 10 mg/body of CDDP and 250 mg/body of 5-FU using arterial infusion were administered. It was discontinued for two days as one course, and 4 courses were basally administered. Patients were divided into 2 groups (6 hours group and 24 hours group) according to the duration of the administration of 5-FU. There were no differences in efficacy rate between the 2 groups (6 hours group, 64%; 24 hours group, 62.5%), but CR (complete response) cases appeared in only the 6 hours group. There were no severe side effects in the 2 groups, but systemic side effects appeared in 6 hours group more often than in 24 hours group. Only in the 24 hours group, 2 patients had the narrowing and obstruction of hepatic artery which was suggested to be caused by intimal injury due to continuous administration of 5-FU. Continuous arterial infusion chemotherapy with CDDP and 5-FU seemed to be effective. Further study on adequate time and volume of administration including pharmacokinetics is needed to enhance the clinical effectiveness of continuous arterial infusion of CDDP and 5-FU.

Aged↗
PubMed1994

Expression of the tyrosinase-encoding gene in a colorless melanophore mutant of the medaka fish, Oryzias latipes.

In the medaka fish Oryzias latipes many mutants for body colors have been isolated. Among them, a colorless melanophore mutant b, carrying b alleles homozygously, has pigmented black eyes but orange-colored skin with amelanotic melanophores, suggesting the presence of a tissue-specific mechanism of melanin formation. To cast light on the molecular basis of the mechanism, we have cloned cDNAs for tyrosinase (Tyr), a key enzyme in melanin biosynthesis, from the wild-type (wt) fish. DNA sequence analysis revealed that all clones encode a protein of 540 amino acids, having five potential glycosylation sites and two copper-binding sites that are characteristic features of Tyr. Genomic DNA blot analysis disclosed that the Tyr gene is present as a single copy in the fish genome. Using a cDNA clone as a probe, RNA blot analysis was carried out. In the wt, the 2.2-kb Tyr mRNA was expressed in eyes and skin but not in liver, corresponding to tissue-specific melanin formation. In the b mutant, contrary to expectation, the mRNA was detected not only in eyes but also in amelanotic skin. Therefore, pigmentation of the skin controlled by b is not directly related to expression of the Tyr gene.

Alleles↗
PubMed1994

Carbon tetrachloride increases sinusoidal efflux of reduced and oxidized glutathione in rats.

To elucidate the significance of the changes in plasma glutathione concentrations associated with carbon tetrachloride (CCl4)-induced liver damage, the changes in the concentrations of reduced (GSH) and oxidized glutathione (GSSG) in plasma as well as in the liver were investigated in rats. In the liver, the concentration of GSH decreased, and that of GSSG increased 24 hr after the intraperitoneal administration of CCl4. In the right atrial plasma, the concentration of both GSH and GSSG increased. The GSH/GSSG ratio in the plasma decreased as did that in the liver. The net sinusoidal efflux of GSH and GSSG from the liver was calculated by subtracting their concentrations in plasma of the infrahepatic inferior vena cava from those of the suprahepatic inferior vena cava. The net efflux of GSH and GSSG started to increase as early as 3-6 hr after CCl4 administration, and reached a plateau 6 and 24 hr after CCl4 administration, respectively. On the other hand, an elongation of prothrombin time and leakage of alanine aminotransferase reached a maximum 24 and 48 hr after CCl4 administration, respectively. Vacuolization in the centri-lobular region and inflammatory infiltration started 3 and 6 hr after CCl4 administration, respectively, and progressed for 48 hr. These results suggest that CCl4 induced an increase in plasma concentrations of GSH as well as GSSG by increasing their efflux from the liver, and that the changes in plasma glutathione status might be a useful and sensitive marker for CCl4-induced liver damage.

Animals↗
PubMed1994

The limiting effect of dichloroacetate on endotoxin-induced liver damage in starved rats.

Dichloroacetate has been shown to have therapeutic effects on sepsis and endotoxin shock and to reduce liver damage in rats intoxicated with ethanol or carbon tetrachloride. In this study, the effect of dichloroacetate on endotoxin hepatitis was investigated. Endotoxin hepatitis was induced by an intraperitoneal coadministration of 50 micrograms/kg lipopolysaccharide from Escherichia coli, and 200 mg/kg D-galactosamine in starved, male Wistar rats. This treatment induced the following changes within 24 hr: an increase in the serum aminotransferase activity, histological alterations of the liver including focal necrosis of liver cells and inflammatory infiltrates, an increase in blood pyruvate and alanine concentrations, and inhibition of starvation ketosis. The intraperitoneal administration of 250 mg/kg dichloroacetate 30 min after the administration of the toxins partially counteracted all of these changes. The administration of dichloroacetate might be useful in coping with hepatic damage as well as lacticemia and cardiovascular depression induced by endotoxins.

Alanine Transaminase↗
PubMed1994

[The study of continuous arterial infusion chemotherapy with 5-FU and CDDP in patients with hepatocellular carcinoma].

Between Feb. 1992 and March in 1994, 14 patients with hepatocellular carcinoma (7: recurrence, 7: unresectable) received continuous arterial infusion of 5-FU and CDDP via implanted reservoir. For the next five days, 10 mg/body of CDDP and 250 mg/body of 5-FU using arterial infusion were administered. It was discontinued for two days, as one course, and 4 courses were basally administered. The duration of the administration was 24 or 6 hours/day. Side effects consisted of nausea or loss of appetite for 7 (50%), suppression of bone marrow for 3 (21%), and they disappeared after the agents were discontinued. However, there were 3 patients with gastro-duodenal ulcer, so careful follow-up was necessary. The efficacy rate was 64% and two-year survival rate was 57% and thus this treatment seemed to be effective. Further study on the duration and dose of the administration is necessary to improve the therapeutic effect and QOL.

Aged↗