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Biomedical subjects

H Himeno

Publications and source records attributed to H Himeno.

At least 73 records · Page 4Linked to original sources
PubMed1992

In vitro study of E.coli tRNA(Arg) and tRNA(Lys) identity elements.

Various tRNA transcripts were constructed to study the identity elements of E.coli tRNA(Arg) and tRNA(Lys). Exchange of the anticodon of the major tRNA(Arg) from ACG to either CCG or CCU did not result in a significant loss of arginine acceptor activity, whereas not only that to UUU but also that to ACA or ACC decreased the activity. Base substitutions and deletion at A20 also impaired the arginine charging activity by over 50-fold. Arginine charging activity was introduced by either substitution of the anticodon from UAC to ACG in tRNA(Val) or from UUU to UCU in tRNA(Lys). Only a single base substitution at the third position of tRNA(Trp) anticodon (CCA) from A to G also gave rise to arginine charging activity, which was elevated to a comparable level to that of the tRNA(Arg) transcript by an additional A20 insertion. Base substitutions of the major tRNA(Arg) at the discriminator position into pyrimidines led to a decrease by factors of three to four. These data show that the third letter of the anticodon G36 or U36 besides the second letter C35 and the A20 in the variable pocket is responsible for the arginine acceptor identity, to which the discriminator base A73 or G73 contributes in an auxiliary fashion. In contrast to the arginine system, the transcript with the wild-type tRNA(Lys) sequence showed only 140-fold lower lysine charging activity than the native tRNA(Lys), suggesting the involvement of base modifications in recognition. Replacement of the anticodon UUU with not only UCU and UAC but also UUA and UUC seriously affected the lysine acceptor activity, and those with GUU and UUG also decreased by factors of 17 and 5, respectively. Introduction of UUU into the anticodons conferred lysine charging activity upon both tRNA(Val) and tRNA(Arg). Substitution of the discriminator base A73 by any of the other bases decreased the lysine acceptor activity by a factor of ten. These results indicate the involvements of all the three bases of the anticodon and A at the discriminator position in lysine specific aminoacylation.

Anticodon↗
PubMed1992

Identity determinants of E. coli threonine tRNA.

To investigate the identity determinants of E. coli threonine tRNA, various transcripts were prepared by in vitro transcription system with T7 RNA polymerase. Substitutions of the anticodon second letter G35 and the third letter U36 to other nucleotides led to a remarkable decrease of threonine charging activity. Charging experiments with a series of anticodon-deletion transcripts also suggest the importance of the G35U36 sequence. A mutation at either the G1-C72 or C2-G71 base pair in the acceptor stem seriously affected the threonine charging activity. These results indicate that the second and third positions of the anticodon and the first and second base pairs in the acceptor stem are the recognition sites of E. coli tRNA(THR) for threonyl-tRNA synthetase. Discriminator base, A73, is not involved in threonine charging activity.

Base Sequence↗
PubMed1992

Administration of interleukin-2 induces major histocompatibility complex class II expression on the biliary epithelial cells, possibly through endogenous interferon-gamma production.

In various organ-specific autoimmune diseases, aberrant expression of major histocompatibility complex class II antigens on each target epithelial cell has been reported. Some researchers have attempted to link this phenomenon to the antigen-presenting capacity and the induction of autoimmunity, whereas others think it might serve as a peripheral mechanism for the induction and the maintenance of self-tolerance in autoreactive T cells. In this study, we showed that intraperitoneal administration of interleukin-2 (1.2 x 10(6) IU/kg) to 4-wk-old male BALB/c mice for 35 consecutive days induced lymphocyte infiltration around bile ducts in the liver and major histocompatibility complex class II expression on biliary epithelial cells, which was immunoelectron microscopically confined to the luminal cell surface. Immunohistochemically, lymphocytes accumulating around bile ducts were mainly T cells, positive for CD3, L3T4 and H-2 class II molecules, and a few of them were positive for Lyt-2 and negative for immunoglobulin. Half of the infiltrates were positive for asialo GM1, and one-third was positive for interferon-gamma. Interferon-gamma-positive, L3T4-positive cells were detected in mirror sections. However, neither the destruction of biliary epithelial cells nor the presence of granulomas was observed. Autoantibodies were serologically undetectable. The existence of interferon-gamma-positive cells in the lesion and the fact that intravenous administration of anti-interferon-gamma twice a week completely inhibited the lymphocyte infiltration and the major histocompatibility complex class II expression on biliary epithelial cells suggested that these changes were induced through endogenous interferon-gamma production.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The role of anticodon bases and the discriminator nucleotide in the recognition of some E. coli tRNAs by their aminoacyl-tRNA synthetases.

The T7 polymerase transcription system was used for in vitro synthesis of unmodified versions of the E. coli tRNA mutants that insert asparagine, cysteine, glycine, histidine, and serine. These tRNAs were used to qualitatively explore the role of some anticodon bases and the discriminator nucleotide in the recognition of tRNA by aminoacyl-tRNA synthetases. Coupled with data from earlier studies, these new results essentially complete a survey of all E. coli tRNAs with respect to the involvement of anticodon bases and the discriminator nucleotide in tRNA recognition. It is found that in the vast majority of tRNAs both of these elements are significant components of tRNA identity. This is not universally true, however. Anticodon sequences are unimportant in tRNA(Ser), tRNA(Leu), and tRNA(Ala) while the discriminator base is inconsequential in tRNA(Ser) and tRNA(Thr). The significance of these results for origin-of-life studies is discussed.

Amino Acyl-tRNA Synthetases↗
PubMed1992

Detection of selenium in generalized and localized argyria: report of four cases with X-ray microanalysis.

Electron microscopic and X-ray microanalytic studies were performed on four cases of argyria; one generalized and three localized. Deposition of electron dense granules was predominantly found on elastic fibers and around basal laminas of secretory portions of eccrine glands, although the amount of deposition was much less in the case of generalized argyria. In all four cases, X-ray microanalysis revealed that the depositions consisted mainly of silver, selenium, and sulfur. The importance of selenium in the detoxification of heavy metals was discussed.

Acupuncture Therapy↗
PubMed1992

Renin gene expression in the adrenal and kidney of patients with primary aldosteronism.

mRNA levels for renin in the adrenal gland and kidney were measured by ribonuclease protection assay (RPA). Renin mRNA was not detected by RPA in aldosteronoma and kidney tissues obtained from two patients with primary aldosteronism (PA). In these patients, the PRA values, plasma concentrations of active renin (ARC), and total renin (TRC = ARC + prorenin) were below the assay limit (less than 0.03 ng/L.s, 2.5 ng/L, and 10 ng/L, respectively). On the other hand, renin mRNA was recognized by RPA in aldosteronoma and kidney tissues obtained from two other patients with PA treated with 50 mg/day spironolactone for more than 2 months. Their TRC values were 49.8 and 16.6 ng/L, but their PRA and ARC were undetectable. Renin mRNA content was greater in normal adrenocortical tissue and in the normal kidneys obtained from three hypertensive patients with renal cell carcinoma. In these patients, the mean values of PRA, ARC, and TRC were 0.28 +/- 0.03 (mean +/- SD) ng/L.s, 18.4 +/- 7.8 ng/L, and 110 +/- 15 ng/L, respectively. This is the first report of the lack of renin gene expression in aldosteronoma and kidney tissues obtained from untreated patients with PA. Furthermore, treatment with spironolactone resulted in an increase in the levels of renin mRNA in the aldosteronoma and kidney tissues of patients with PA.

Adrenal Cortex↗
PubMed1992

In vitro study of E. coli tRNA identity elements.

Various tRNA transcripts were constructed to study the identity elements of E. coli tRNAs (Arg, Lys, Ala, Trp, Thr, Gly, Ser, Asn, Cys, His). Anticodon are involved in the identity elements in these tRNA species except the case of tRNA(Ala) and tRNA(Ser). Especially, the second and third positions of the anticodon are the recognition sites of E. coli tRNA(Arg), tRNA(Lys) and tRNA(Thr) for their cognate aminoacyl-tRNA synthetases. Discriminator base is an identity determinant of the above examined tRNAs except tRNA(Thr) and tRNA(Ser). In some cases, acceptor stem (Thr, Gly, His) and variable pocket (Arg, Ala) are considered to be the recognition elements.

Amino Acids↗
PubMed1991

Identity determinants of E. coli tryptophan tRNA.

The first base pair of the acceptor stem A1-U72 and the discriminator base G73, as well as the anticodon nucleotides, characterize the tryptophan tRNA in E. coli. To determine the contribution of these nucleotides to the tryptophan acceptor activity, various transcripts of E. coli tryptophan tRNA mutants were constructed. Substitutions of the discriminator base G73, which is conserved within prokaryotic tryptophan tRNAs, impaired aminoacylation with tryptophan. Substitutions of other purine-pyrimidine pairs for A1-U72 revealed that only U72 weakly contributed to recognition by tryptophanyl-tRNA synthetase. The E. coli aspartic acid tRNA transcript introducing the tryptophan anticodon CCA showed almost the same tryptophan charging activity as the tryptophan tRNA transcript possessing a G1-C72 base pair. Only a low activity was detected in the mutant tryptophan tRNA transcript possessing a set of G1-C72 and A73, which is observed in eukaryotic tryptophan tRNAs. These results indicate that the anticodon and G73 are major identity determinants of tryptophan tRNA in E. coli, whereas the A1-U72 base pair is only a weak recognition element.

Anticodon↗
PubMed1991

Identity determinants of E. coli tRNA(Val).

In order to study the identity elements of valine tRNA, various transcripts of E. coli valine tRNA mutants were constructed. Both mutations at the second letter A35 of the anticodon and at the discriminator base A73 seriously damaged valine charging activity. Mutations at either the G3-C70 or U4-A69 base pairs in the acceptor stem also affected the activity. Only one nucleotide substitution of the second letter G35 of the anticodon with A35 brought an 18% valine charging activity into alanine tRNA, which acquired an almost full charging activity with valine by introducing an additional change at those two base pairs in the acceptor stem. These results indicate that the second letter A35 of the anticodon, discriminator base and acceptor stem are involved in recognition by valyl-tRNA synthetase.

Base Composition↗
PubMed1991

Strand-specific nucleotide composition bias in echinoderm and vertebrate mitochondrial genomes.

The gene organization of starfish mitochondrial DNA is identical with that of the sea urchin counterpart except for a reported inversion of an approximately 4.6-kb segment containing two structural genes for NADH dehydrogenase subunits 1 and 2 (ND 1 and ND 2). When the codon usage of each structural gene in starfish, sea urchin, and vertebrate mitochondrial DNAs is examined, it is striking that codons ending in T and G are preferentially used more for heavy strand-encoded genes, including starfish ND 1 and ND 2, than for light strand-encoded genes, including sea urchin ND 1 and ND 2. On the contrary, codons ending in A and C are preferentially used for the light strand-encoded genes rather than for the heavy strand-encoded ones. Moreover, G-U base pairs are more frequently found in the possible secondary structures of heavy strand-encoded tRNAs than in those of light strand-encoded tRNAs. These observations suggest the existence of a certain constraint operating on mitochondrial genomes from various animal phyla, which results in the accumulation of G and T on one strand, and A and C on the other.

Amino Acid Sequence↗
PubMed1991

Unilateral aminoacylation specificity between bovine mitochondria and eubacteria.

The present study shows unilateral aminoacylation specificity between bovine mitochondria and eubacteria (Escherichia coli and Thermus thermophilus) in five amino acid-specific aminoacylation systems. Mitochondrial synthetases were capable of charging eubacterial tRNA as well as mitochondrial tRNA, whereas eubacterial synthetases did not efficiently charge mitochondrial tRNA. Mitochondrial phenylalanyl-, threonyl-, arginyl-, and lysyl-tRNA synthetases were shown to charge and discriminate cognate E. coli tRNA species from noncognate ones strictly, as did the corresponding E. coli synthetases. By contrast, mitochondrial seryl-tRNA synthetase not only charged cognate E. coli serine tRNA species but also extensively misacylated noncognate E. coli tRNA species. These results suggest a certain conservation of tRNA recognition mechanisms between the mitochondrial and E. coli aminoacyl-tRNA synthetases in that anticodon sequences are most likely to be recognized by the former four synthetases, but not sufficiently by the seryl-tRNA synthetase. The unilaterality in aminoacylation may imply that tRNA recognition mechanisms of the mitochondrial synthetases have evolved to be, to some extent, simpler than their eubacterial counterparts in response to simplifications in the species-number and the structural elements of animal mitochondrial tRNAs.

Amino Acyl-tRNA Synthetases↗
PubMed1991

Measurement of plasma total renin by the anti-human renin monoclonal antibodies.

The authors evaluated the assay performances and clinical usefulness of a newly developed solid phase radioimmunoassay (RIA) for total renin concentration (TRC) in human plasma. The direct total renin RIA was performed by a sandwich technique with a pair of anti-human renin monoclonal antibodies. Renin activation with trypsin did not change TRC. The RIA showed satisfactory assay performances and demonstrated full compatibility with a direct RIA-kit for active renin concentration (ARC) in human plasma. The values of TRC were 105.3 +/- 8.6 pg/mL in normal subjects and 136.5 +/- 14.6 pg/mL in patients with essential hypertension. The values of TRC and the ratios of ARC to TRC were high in patients with renovascular hypertension and were low in patients with primary aldosteronism. Although the TRC value in diabetic patients was 134.4 +/- 14.8 pg/mL, the ratio of ARC to TRC was low. The RIA procedure was simple since prior purification or activation of renin was not required. These results suggest that the total renin RIA and its combined use with the active renin RIA may be helpful in understanding the renin-angiotensin system in human plasma.

Antibodies, Monoclonal↗
PubMed1991

Identity determinants of E. coli tRNAs.

Identity determinants of E. coli tRNA(Val) and three class II tRNAs, tRNA(Ser), tRNA(Tyr) and tRNA(Leu), are studied by using various variants of tRNA transcripts. Anticodon, discriminator base and acceptor stem are involved in the identity elements for tRNA(Val). Discrimination among class II tRNAs are considered to be dependent on the bases at positions 2, 71 and 73 as well as their different tertiary structures including the long variable arm.

Codon↗
PubMed1990

Conversion of aminoacylation specificity from tRNA(Tyr) to tRNA(Ser) in vitro.

The discrimination mechanism between tRNA(Ser) and tRNA(Tyr) was studied using various in vitro transcripts of E. coli tRNATyr variants. The insertion of only two nucleotides into the variable stem of tRNA(Tyr) generates serine charging activity. The acceptor activities of some of the tRNA(Tyr) mutants with insertions in the long variable arm were enhanced by changes in nucleotides at positions 9 and/or 20B, which are possible elements for dictating the orientation of the long variable arm. These findings suggest that the long variable arm is involved in recognition by seryl-tRNA synthetase in spite of sequence and length variations shown within tRNA(Ser) isoacceptors, and eventually serves as a determinant for selection from other tRNA species. Changing the anticodon from GUA to the serine anticodon GGA resulted in a marked decrease in tyrosine charging activity, but this mutant did not show any serine charging activity. The discriminator base, the fourth base from the 3' end of tRNA, was also important for aminoacylation with tyrosine. Complete specificity change in vitro was facilitated by insertion of three nucleotides into the variable arm plus two nucleotide changes at positions 9 and 73.

Acylation↗
PubMed1990

Assessment of bilirubin clearance capacity of a newly developed ion-exchange adsorption column and its possible use as a supportive therapy in hepatorenal syndrome.

We assessed the bilirubin reduction capacity of three different types of devices in vitro: a high-permeable membrane column for double-filtration plasmapheresis (DFP) (Evaflux 2A, Kuraray, Japan), and non-coated charcoal column for hemoperfusion (HP) (N-180, Asahi Medical, Japan), and ion-exchange columns for plasma adsorption (PA) (BR-350, Asahi Medical, Japan, and B-001, Kuraray, Japan). A column for DFP reduced the concentration of low-molecular proteins effectively such as plasma bilirubin and bile acids in an albumin-dependent manner. A charcoal column adsorbed low-molecular substances preferentially. But in these two columns, the loss of fibrinogen is a limiting factor for determining the processing plasma volume. Ion-exchange columns for PA adsorbed bile acids, disconjugated bilirubin, and monoconjugated bilirubin more efficiently compared with delta-bilirubin and unconjugated bilirubin. Pretreatment of the column with heparin reduced the loss of fibrinogen to less than 10%. We applied the BR-350 ion-exchange column in vivo for treatment of three patients with hyperbilirubinemia. After treatment, an alcoholic hepatitis patient with the hepatorenal syndrome (HRS) recovered from acute renal failure. However, in a patient with primary biliary cirrhosis and in a patient with fulminant hepatitis, the decrease of serum bilirubin was transient and no obvious beneficial responses were noted. The capacity and ability of the BR-350 column to adsorb plasma bilirubin was shown sufficient to treat deeply jaundiced patients, because 4 liters of the plasma of a patient with 108 mg/dl of initial total bilirubin concentration was able to be processed continuously without an obvious decrease in bilirubin adsorption capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1990

The genetic code of a squid mitochondrial gene.

Cytochrome oxidase subunit I gene of a squid (Mollusca), Doryteuthis mitochondrial genome was sequenced. Comparison with the nucleotide sequence and the deduced amino acid sequence of other animal mitochondria suggests that the squid mitochondria has a variation in the genetic code; UGA codes for tryptophan, AUA for methionine and AGA/G for serine. This situation is similar to the case of Drosophila or Ascaris mitochondria.

Amino Acid Sequence↗
PubMed1989

Role of the extra G-C pair at the end of the acceptor stem of tRNA(His) in aminoacylation.

All sequenced histidine tRNAs have one additional nucleotide at the 5' end compared with other tRNA species. To investigate the role of this unique structure in aminoacylation, we constructed in vitro transcripts corresponding to the E. coli histidine tRNA sequence and its variants at the G-1-C73 base pair, by using T7 RNA polymerase transcription system. A transcript having a wild-type sequence with no modified bases was a good substrate for histidyl-tRNA synthetase (HisRS), and aminoacylation activity was affected by introduction of a triphosphate at the 5' terminus. Base replacements at position 73 caused a marked decrease of Vmax, and deletion and substitution of the G-1 had a remarkable effect on the aminoacylation. A mutant having an A-1-U73 pair was also not a good substrate for HisRS. Comparison among G-1-deficient mutants showed that A was preferable rather than C as the base at position 73. These data demonstrate that the set of the G-1-C73 pair at the end of the acceptor stem of histidine tRNA is crucial for the catalytic process of aminoacylation.

Acylation↗