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Biomedical subjects

H Fukuhara

Publications and source records attributed to H Fukuhara.

At least 37 records · Page 2Linked to original sources
PubMed2000

Disruption of the MRP-L23 gene encoding the mitochondrial ribosomal protein L23 is lethal for Kluyveromyces lactis but not for Saccharomyces cerevisiae.

The Kluyveromyces lactis nuclear gene, MRP-L23, encodes a polypeptide of 155 amino acids that shares 70% and 43% identity to the ribosomal proteins L23 and L13 of Saccharomyces cerevisiae and Escherichia coli. The deduced protein, designated K1L23, is a likely component of the large subunit of mitochondrial ribosomes as it can complement the respiratory deficient phenotype of a S. cerevisiae mrp-L23 mutant. As in S. cerevisiae, KlMRP-L23 is essential for respiratory growth of K. lactis because disruption of the gene in a "petite-positive" strain carrying a rho o-lethality suppressor atp mutation rendered cells unable to grow on a nonfermentable carbon source. However, in contrast to S. cerevisiae, disruption of MRP-L23 in wild type K. lactis is lethal. Meiotic segregants of K. lactis with a disrupted MRP-L23 allele form microcolonies with cell numbers varying from 32 to 300. These data clearly indicate an essential role of mitochondrial protein synthesis for viability of the petite-negative yeast K. lactis.

Amino Acid Sequence↗
PubMed2000

Construction of human-rodent hybrid cells containing single transferable fragments of human chromosome 10p.

The introduction of chromosome 10p into human glioblastoma or prostate cancer cells has been demonstrated to suppress their malignant phenotype, suggesting the presence of glioma or prostate tumor suppressor genes on 10p. As a resource for the fine mapping of these genes, a series of human-rodent hybrid cell lines containing single transferable fragments (STFs) of 10p were constructed. Normal chromosome 10 tagged with a neomycin-resistance gene on its short arm was fragmented by gamma-irradiation of 5-10krad, transferred into mouse L cells or Chinese hamster ovary cells by microcell-mediated chromosome transfer (MMCT), and then selected against G418. Thirty-three independent rodent-human hybrids carrying various-sized STFs were obtained. Polymerase chain reaction (PCR)-based genotyping revealed that these STFs contained the whole, or portions, of a 43-cM region on 10p14-pter and could be defined by 19 sequence-tagged-site (STS) markers. Using this panel of hybrids as donors for further MMCT, genes on the refined fragments could be transferred into other cells. This hybrid panel would therefore be a useful resource for the fine mapping of the genes on 10p14-pter to segments of about 2.4 cM by functional complementation.

Animals↗
PubMed2000

Successful radiofrequency catheter ablation of left ventricular tachycardia following surgical correction of tetralogy of Fallot.

A 13-year-old boy had recurrent ventricular tachycardia following surgical correction of tetralogy of Fallot. Pharmacological management with multiple antiarrhythmic drugs failed, and the patient underwent electrophysiological evaluation. A reentrant tachycardia involving a slowly conducting region in the left ventricular outflow tract was demonstrated. We performed radiofrequency catheter ablation after identifying the essential components of the reentrant circuit. The ventricular tachycardia could no longer be induced and did not recur spontaneously during a 13-month follow-up.

Adolescent↗
PubMed2000

Secreted phytase activities of yeasts.

The enzyme phytase dephosphorylates phytin (inositol hexaphosphate), a major phosphate reserve in plants. We found that a large number of yeast species secreted a phytase. Several species were identified as high phytase producers. The yeast enzymes had an optimal activity at pH 4-5 and generally a very high optimal temperature, ranging from 60 degrees C to 80 degrees C.

6-Phytase↗
PubMed1999

Linear DNA plasmid pPK2 of Pichia kluyveri: distinction between cytoplasmic and mitochondrial linear plasmids in yeasts.

The linear plasmids frequently found in plants and filamentous fungi are associated with mitochondria or chloroplasts. In contrast, all the linear plasmids known in yeasts are cytoplasmic elements. From a strain of the yeast Pichia kluyveri, we have isolated a new linear plasmid, pPK2, which was found to be associated with mitochondria. This 7.1 kilobase pairs-long DNA contained only two genes, which code for DNA and RNA polymerases, as judged from their nucleotide sequences translated by a mitochondrial genetic code. When we examined several recently isolated yeast plasmids for their subcellular localization, we found that two linear plasmids, pPH1 from Pichia heedii, as well as pPK1 from another strain of P. kluyveri, were also localized in mitochondria. These plasmids are the first examples of mitochondria-associated linear plasmids in yeast. All other linear plasmids we examined were of cytoplasmic origin. Whilst the cytoplasmic type linear plasmids were efficiently eliminated by ultraviolet irradiation of host cells, the mitochondria-associated plasmids were highly resistant. The mitochondrial pPK2 plasmid was rapidly lost by treatment of the host cells with ethidum bromide.

Amino Acid Sequence↗
PubMed1999

Mitochondrial telomere-binding protein from Candida parapsilosis suggests an evolutionary adaptation of a nonspecific single-stranded DNA-binding protein.

The mitochondrial genome in a number of organisms is represented by linear DNA molecules with defined terminal structures. The telomeres of linear mitochondrial DNA (mtDNA) of yeast Candida parapsilosis consist of tandem arrays of large repetitive units possessing single-stranded 5' extension of about 110 nucleotides. Recently we identified the first mitochondrial telomere-binding protein (mtTBP) that specifically binds a sequence derived from the extreme end of C. parapsilosis linear mtDNA and protects it from attack by various DNA-modifying enzymes (Tomáska, L'., Nosek, J., and Fukuhara, H. (1997) J. Biol. Chem. 272, 3049-3059). Here we report the isolation of MTP1, the gene encoding mtTBP of C. parapsilosis. Sequence analysis revealed that mtTBP shares homology with several bacterial and mitochondrial single-stranded DNA-binding proteins that nonspecifically bind to single-stranded DNA with high affinity. Recombinant mtTBP displays a preference for the telomeric 5' overhang of C. parapsilosis mtDNA. The heterologous expression of a mtTBP-GFP fusion protein resulted in its localization to the mitochondria but was unable to functionally substitute for the loss of the S. cerevisiae homologue Rimlp. Analysis of the MTP1 gene and its translation product mtTBP may provide an insight into the evolutionary origin of linear mitochondrial genomes and the role it plays in their replication and maintenance.

Amino Acid Sequence↗
PubMed1998

Linear mitochondrial genomes: 30 years down the line.

At variance with the earlier belief that mitochondrial genomes are represented by circular DNA molecules, a large number of organisms have been found to carry linear mitochondrial DNA. Studies of linear mitochondrial genomes might provide a novel view on the evolutionary history of organelle genomes and contribute to delineating mechanisms of maintenance and functioning of telomeres. Because linear mitochondrial DNA is present in a number of human pathogens, its replication mechanisms might become a target for drugs that would not interfere with replication of human circular mitochondrial DNA.

Animals↗
PubMed1998

[The left ventriculectomy (Batista procedure) in a patient of the dilated cardiomyopathy: a report of the first successful case in Japan].

We presented a case of 18-year-old male with dilated cardiomyopathy undergoing surgical left ventricular volume reduction (Batista procedure). He seemed to be the first successful survivor after the procedure in Japan. In the follow up study, cardiac function and clinical status of the patient have been moderately improved. Batista procedure seems to be an attractive choice to treat end-stage heart failure in Japan where the option of treatment for this particular situation is limited.

Adolescent↗
PubMed1997

Identification of a putative mitochondrial telomere-binding protein of the yeast Candida parapsilosis.

Terminal segments (telomeres) of linear mitochondrial DNA (mtDNA) molecules of the yeast Candida parapsilosis consist of large sequence units repeated in tandem. The extreme ends of mtDNA terminate with a 5' single-stranded overhang of about 110 nucleotides. We identified and purified a mitochondrial telomere-binding protein (mtTBP) that specifically recognizes a synthetic oligonucleotide derived from the extreme end of this linear mtDNA. MtTBP is highly resistant to protease and heat treatments, and it protects the telomeric probe from degradation by various DNA-modifying enzymes. Resistance of the complex to bacterial alkaline phosphatase suggests that mtTBP binds the very end of the molecule. We purified mtTBP to near homogeneity using DNA affinity chromatography based on the telomeric oligonucleotide covalently bound to Sepharose. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the purified fractions revealed the presence of a protein with an apparent molecular mass of approximately 15 kDa. UV cross-linking and gel filtration chromatography experiments suggested that native mtTBP is probably a homo-oligomer. MtTBP of C. parapsilosis is the first identified protein that specifically binds to telomeres of linear mitochondrial DNA.

Base Sequence↗
PubMed1997

The Kluyveromyces lactis equivalent of casein kinase I is required for the transcription of the gene encoding the low-affinity glucose permease.

The RAG8 gene of Kluyveromyces lactis, which is one of the genes controlling the expression of the low-affinity carrier gene RAG1, has been cloned by in vivo complementation of the rag8 mutation. The sequence of Rag8p (535 amino acids), deduced from the nucleotide sequence of the cloned RAG8 gene, has been found to share a high degree of identity with the two casein kinases I of Saccharomyces cerevisiae, Yck1p and Yck2p, encoded by YCK1 and YCK2: the proteins are 65-66%, identical overall and show 89-90% identity in the kinase domain. The finding that the RAG8 gene of K. lactis cloned in a centromeric vector was able to complement the growth defect of a yck1 delta yck2(ts) mutant of S. cerevisiae strongly suggested that Rag8p is a casein kinase I. In contrast to the S. cerevisiae homologs, the RAG8 gene of K. lactis seems to be an essential single-copy gene, as shown by Southern blot experiments and the lethality of the rag8 null mutation. Northern blot analysis showed that the transcription of the RAG8 gene was higher on glucose media than in cells grown on a non-fermentable carbon source.

Amino Acid Sequence↗
PubMed1997

A circular plasmid from the yeast Torulaspora delbrueckii.

A new member of the 2-micron family of plasmids, named pTD1, was found in the yeast Torulaspora delbrueckii, a widespread yeast associated with food. Nucleotide sequences revealed the presence of a pair of inverted repeats and three open reading frames, one of which is a homologue of the FLP recombinase gene of 2-micron plasmid. An ARS region was identified, by replication in Saccharomyces cerevisiae and T. delbrueckii, near one of the inverted repeats. By the use of pTD1 derivatives and auxotrophic mutant hosts an efficient host-vector system was established for T. delbrueckii. So far, the 2-micron family of plasmids is restricted to four closely related genera (Q6 group): Saccharomyces, Zygosaccharomyces, Kluyveromyces, and Torulaspora. After a survey of 2500 strains belonging to about 500 species (80 genera) of yeast, no circular plasmids were found in other genera.

Ascomycota↗
PubMed1997

[A case of hormone-refractory prostate cancer responsive to low-dose prednisolone therapy].

A 67-year-old man with hormone-refractory (stage D2) prostate cancer was admitted to the hospital because of general malaise and bone pain. The patient had been receiving hormonal therapy, which was discontinued after admission. Instead, 10 mg per day of prednisolone was administered orally. His symptoms improved, and the serum prostate specific antigen (PSA) level decreased markedly. After 18 weeks of treatment with prednisolone, the serum PSA level rose again, and bone pain worsened. The patient died of cancer one month later.

Aged↗
PubMed1997

[Aspiration pneumonia during the endotracheal intubation on the occasion of bladder perforation by TUR].

We report on two cases of aspiration pneumonia which developed during the endotracheal intubation after bladder perforation during TUR. The first case was a 79 y.o. male, who underwent TUR-P and lithotripsy under spinal and epidural anesthesia. The second case was a 69 y.o. male, who had undergone TUR-Bt under nitrous oxide-oxygen-enflurane anesthesia. General anesthesia was selected to perform an laparotomy when the diagnosis was made. They vomited a considerable amount of gastric content just after giving the drugs for induction. The chest X-rays revealed signs of aspiration pneumonia. These X-ray findings improved in a week using antibiotic therapy. Although TUR is performed as scheduled, vomiting may occur in the case of unexpected bladder perforation, which can cause aspiration pneumonia. In such emergency, we should insert a nasal tube before induction, press the cricoid (crush induction), or intubate with the patient awake.

Aged↗
PubMed1996

RAG3 gene and transcriptional regulation of the pyruvate decarboxylase gene in Kluyveromyces lactis.

The RAG3 gene has been cloned from a Kluyveromyces lactis genomic library by complementation of the rag3 mutation, which shows impaired fermentative growth on glucose in the presence of respiratory inhibitors. From the nucleotide sequence of the cloned DNA, which contained an open reading frame of 765 codons, the predicted protein is 49.5% identical to the Pdc2 protein of Saccharomyces cerevisiae, a regulator of pyruvate decarboxylase in this yeast. Measurement of the pyruvate decarboxylase activity in the original rag3-1 mutant and in the null mutant confirmed that the RAG3 gene is involved in pyruvate decarboxylase synthesis in K. lactis. The effect is exerted at the mRNA level of the pyruvate decarboxylase structural gene KIPDCA. Despite analogies between the RAG3 gene of K. lactis and the PDC2 gene of S. cerevisiae, these genes were unable to reciprocally complement.

Amino Acid Sequence↗
PubMed1996

Glucose uptake in Kluyveromyces lactis: role of the HGT1 gene in glucose transport.

A gene for high-affinity glucose transport, HGT1, has been isolated from the lactose-assimilating yeast Kluyveromyces lactis. Disruption strains showed much-reduced uptake of glucose at low concentrations and growth was particularly affected in low-glucose medium. The HGT1 nucleotide sequence implies that it encodes a typical transmembrane protein with 12 hydrophobic domains and with 26 to 31% amino acid identity with the Hxtp family of glucose transport elements in Saccharomyces cerevisiae. Expression is constitutive (in contrast to RAG1, the major gene for low-affinity glucose uptake in K. lactis) and is controlled by several genes also known to affect expression of RAG1. These include RAG5 (which codes for the single hexokinase of K. lactis), which is required for HGT1 transcription, and RAG4, which has a negative effect. The double mutant deltahgt1deltarag1 showed further reduced glucose uptake but still grew quite well on 2% glucose and was not completely impaired even on 0.1% glucose.

Amino Acid Sequence↗
PubMed1996

[Ultradian rhythms in the nasal cycle as measured by a new method].

Various methods have been conventionally applied for studies of the nasal cycle. Most of these studies have been through either clinical observations by rhinologists or by the use of physiological apparatuses. The purposes of the present study are to develop a different and simplified technique for measuring the nasal cycle and to determine the extent to which the new technique works with actual cases. Five adult subjects were required to hold a 8 x 6 mirror horizontally under the nostrilsin and to breathe through the nose with the mouth closed. The length of time required for the exhalation vapor to condense on the mirror was measured every 15 minutes from 9 a.m. to 5 p.m. LR index scores (L-R/L+R) were calculated on the bases of left and right time, and maximum entropy method spectral analysis was used to determine the nasal cycle. The results showed that three of the subjects demonstrated significant periodicities equivalent to about three or four hour ultradian rhythms. Some of the problems with individual differences and with this new method were discussed.

Activity Cycles↗
PubMed1995

Linear DNA plasmids of yeasts.

Linear DNA plasmids are common among filamentous fungi and plants in which they are generally associated with mitochondria. In contrast, the linear DNA plasmids of yeast appear to be cytoplasmic and to have a specific genetic organization. In these respects the yeast linear plasmids can be regarded as a separate group of plasmids. A survey of plasmids among about 1800 strains covering practically all the currently accepted species of yeast (about 600) has provided a preliminary, overall view of the nature and frequency of yeast plasmids. Linear DNA plasmids were found at a frequency of 1-2%, with more than 20 cases of new linear plasmids discovered in a large variety of species. The same survey showed that circular DNA plasmids are characteristically confined to a few genera and species. The linear DNAs have many features in common with the linear killer DNAs of Kluyveromyces lactis and form a large family of multicopy, small DNAs disseminated among yeast species.

DNA, Mitochondrial↗