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Biomedical subjects

H Himeno

Publications and source records attributed to H Himeno.

At least 55 records · Page 3Linked to original sources
PubMed1994

tRNA-like structures in 10Sa RNAs of Mycoplasma capricolum and Bacillus subtilis.

The stable RNAs, whose sequences are homologous to 10Sa RNA of Escherichia coli, have been isolated from Mycoplasma capricolum and Bacillus subtilis, both belonging to the Gram-positive bacterial group. The total nucleotide sequences of the RNAs have been determined by partial RNA sequencing and DNA sequencing of their genes. A comparison of the sequences, together with those of other bacterial 10Sa RNAs so far known, has shown that the 5'- and 3'-end sequences are well conserved among species, while the central parts reveal little homologies. Unexpectedly, the conserved 5'- and 3'-regions can be folded in a common tRNA-like structure containing an amino acid-acceptor stem and a T phi C-stem/loop. The 3'-terminal CCA sequence of B.subtilis 10Sa RNA is not encoded on the DNA, but is added after transcription. Furthermore, the RNA is aminoacylatable with alanine in vitro, and binds to the 70S ribosome in vivo.

Acylation↗
PubMed1994

Escherichia coli seryl-tRNA synthetase recognizes tRNA(Ser) by its characteristic tertiary structure.

To investigate the sequence requirements of Escherichia coli tRNA(Ser) for recognition by seryl-tRNA synthetase, various mutants of unmodified tRNA(Ser) were constructed. Substitution of G2.C71 by C2.G71, but not by A2.U71 or U2.A71, impaired the serine-accepting activity, indicating that this position is not involved in recognition by seryl-tRNA synthetase, but contributes to discrimination from other tRNAs processing C2.G71 such as tRNA(Leu). Other nucleotides characteristic of tRNA(Ser), including the discriminator base, were not involved in recognition by seryl-tRNA synthetase. The anticodon was not involved, as suggested by its sequence variety within the isoacceptors. The long variable arm composed of over ten nucleotides, which is a characteristic feature of tRNA(Ser) together with tRNA(Leu) and tRNA(Tyr), was stem-length-specifically, but not sequence-specifically, important for recognition. In order to introduce a sufficient serine-accepting activity to a tRNA(1LEU) transcript in vitro, besides the change from C2.G71 to G2.C71, the following elements had to be changed to those characteristic of tRNA(Ser): the sequence in the D-loop, the stem pairing pattern of the variable arm, the tertiary base-pair 15.48 and the nucleotide at position 59 in the T psi C-loop. None of the nucleotides at these changed positions was involved in base-specific recognition, indicating that seryl-tRNA synthetase selectively recognizes tRNA(Ser) on the basis of its characteristic tertiary structure rather than the nucleotides specific to tRNA(Ser).

Base Sequence↗
PubMed1994

Hitherto unrecognized arterioles within hepatocellular carcinoma.

The distribution of blood vessels in human hepatocellular carcinoma was studied with the anti-a-smooth muscle actin monoclonal antibody by light and electron microscopy, and with morphometric analysis. a-Smooth muscle actin-positive arterioles were never observed in lobules or pseudolobules of non-cancerous areas, but were frequently seen within hepatocellular carcinomas. Morphometric analysis revealed that most of these arterioles measured between 10 and 25 microns in diameter. The morphology of intratumoural arterioles differed considerably from that of conventional arteries in the portal tracts of the non-cancerous area. The presence of abundant intratumoural arterioles can explain the angiographic hypervascularity of hepatocellular carcinoma and provides a pathological basis for its susceptibility to hypoxia and for arterial embolization as a therapeutic strategy.

Adult↗
PubMed1994

Immunoelectron microscopic observations on Leu-7 positive cells in virus-related chronic liver diseases.

We investigated the liver biopsies of 78 patients with hepatitis virus-related chronic liver diseases (B type; 14 patients, C type; 64 patients) by immunoelectron microscopy with the Leu-7 monoclonal antibody in order to determine the association of NK/K cells in virus-related chronic liver diseases. Most Leu-7 positive cells in the liver had the Pit cell morphology but a few Pit cells were Leu-7 negative. A few Leu-7 positive cells had neither Pit cell nor typical T cell morphology. No ultrastructural difference was observed in Leu-7 positive cells between hepatitis B virus- and hepatitis C virus-related chronic liver diseases. Regardless of virus type and hepatitis activity, the fine morphology of extravascular Leu-7 positive cells differed considerably from intravascular cells. Leu-7 positive cells were regularly seen in the cellular infiltrates but the ratio of Leu-7 positive cells/whole infiltrates was low. There was no correlation between the inflammatory activity of the disease and the level of Leu-7 positive cell infiltration. A virus aetiology (hepatitis-C or hepatitis-B) did not affect Leu-7 positive cell infiltration. We conclude that NK cells play only a small role in the pathogenesis of hepatitis B virus or hepatitis C virus-related hepatocytolysis, during the chronic stage.

Adult↗
PubMed1994

Immunohistochemical identification of Ito cells and their myofibroblastic transformation in adult human liver.

To identify Ito cells in normal and pathological adult human livers, immunohistochemical studies were performed by the avidin-biotin-peroxidase complex method using monoclonal antibodies for alpha-smooth muscle actin (ASMA), desmin, and vimentin. Fifty one needle biopsies, 7 surgically resected specimens, and 5 autopsy specimens were studied. In the normal adult liver vascular smooth muscle cells and pericytes, together with perisinusoidal cells with thin cytoplasmic processes were positive for ASMA. These latter cells formed a loose and discontinuous layer along the sinusoidal walls. Immunoelectron microscopy showed that the ASMA-positive perisinusoidal cells were Ito cells containing fat droplets. The other sinusoidal lining cells were negative for ASMA. In chronic liver disease, ASMA-positive Ito cells showed an increase in number, size, and the intensity of immunostaining in areas of piece-meal necrosis), and formed a continuous cellular network. These cells were dendritic in shape with irregularly elongated cytoplasmic processes and contained an increased amount of microfilaments, in association with loss of the characteristic fat droplets. Thus, their ultrastructural features corresponded to those of myofibroblastic cells. Ito cells showed no staining for desmin in both normal and pathological livers. These results indicate that immunohistochemistry using an anti-ASMA antibody is a sensitive and reliable method for the identification of both normal and transformed Ito cells in adult human livers.

Actins↗
PubMed1994

Alpha-smooth muscle actin-positive perisinusoidal stromal cells in human hepatocellular carcinoma.

The purpose of this study is to clarify the morphological characteristics and functional significance of the perisinusoidal stromal cells in hepatocellular carcinoma. The liver specimens surgically resected from 24 patients with hepatocellular carcinoma were studied by electron microscopy and immunohistochemistry using monoclonal antibodies against alpha-smooth muscle actin, vimentin and desmin. In the tissue space between endothelial cells and trabeculae of cancer cells, the stromal cells were frequently found. They were strongly positive for alpha-smooth muscle actin, weakly and less frequently positive for vimentin but negative for desmin. They varied in shape, size and distribution, stretching cytoplasmic processes and occasionally surrounding the trabeculae of cancer cells. They contained considerable amounts of microfilaments that were positive for alpha-smooth muscle actin and condensed in cell periphery. Along the cell membrane, the short dense areas and pinocytotic vesicles were seen. The external lamina incompletely invested the stromal cells. They were always surrounded by amorphous material. In the granulation tissue and fibrotic areas around necrotic cancer tissue, they were increased in size and number. On the other hand, immunohistochemically and ultrastructurally, they closely resembled the Ito cells in the piecemeal necrosis that showed myofibroblastic transformation. These results suggest that the perisinusoidal stromal cells in nonnecrotic cancer tissue produce the extracellular matrix in the tissue space and maintain the cancerous trabecular structure. After necrosis of cancer tissue, they may become activated and actively participate in the fibrosis.

Actins↗
PubMed1994

Susceptibility to neonatal streptozotocin-induced diabetes in spontaneously hypertensive rats.

We studied the difference in the susceptibility to neonatal streptozotocin (STZ) diabetes between spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Two-day-old female SHR and WKY were injected intraperitoneally with 75.0 mg/kg of STZ or vehicle for control. Hyperglycemia developed in both strains at 4 days of age, but SHR were more hyperglycemic. Overt hyperglycemia developed in SHR with aging after a partial recovery from initial hyperglycemia at 10 days of age, whereas WKY did not develop significant hyperglycemia except shortly after STZ treatment. Percentage of insulin-positive B cells in total islet cells and pancreatic immunoreactive insulin (IRI) content were measured at 4 days, 10 days, 4 weeks, and 12 weeks of age. B cells per islet and pancreatic IRI content were significantly reduced in STZ-treated groups as compared with control in both SHR and WKY at 4 days of age, but later they increased significantly with aging in both strains. However, the reduction in pancreatic IRI content relative to control was significantly greater in SHR than in WKY from 4 days (-94.5 +/- 3.5%, -84.1 +/- 4.8%; p < 0.01) to 12 weeks (-97.1 +/- 2.1%, -28.0 +/- 2.5%; p < 0.05), and the reduction in B cells per islet was also greater in SHR at 4 weeks of age. These results indicated that the initial destruction of pancreatic B cells induced by STZ was greater, and the following regeneration was less in SHR than in WKY. The association of the susceptibility to neonatal STZ diabetes with the development of genetic hypertension in SHR remained to be elucidated.

Animals↗
PubMed1994

Angiotensin II alters aortic fibronectin independently of hypertension.

We performed these studies to assess the potential role of hemodynamic forces in mediating the changes in aortic fibronectin mRNA expression that occur in the rat in response to angiotensin II administration. With the use of an acute hypertensive model involving a 3-day infusion with a pressor dose of angiotensin II given by osmotic minipump, a selective increase in fibronectin mRNA expression but not of several other extracellular matrix genes was documented. This change was inhibited by losartan, indicating the importance of angiotensin receptors in the response. Prazosin, hydralazine, or L-arginine added to the drinking water all lowered the angiotensin II-induced increase in blood pressure but did not attenuate the increase in fibronectin mRNA expression. Angiotensin-converting enzyme inhibition using trandolapril did reduce fibronectin mRNA in the angiotensin II-infusion model, despite an inability to reduce blood pressure, whereas when angiotensin I was infused, quinapril lowered both blood pressure and fibronectin expression even at doses that did not completely normalize blood pressure. These studies suggest that angiotensin II induced an increase in aortic fibronectin mRNA that was not dependent solely on blood pressure.

Angiotensin II↗
PubMed1994

Effect of aging on glucose tolerance in spontaneously hypertensive rats.

We studied the age-related changes of glucose tolerance in female spontaneously hypertensive rats (SHR) that did not become obese with aging. Oral glucose tolerance test was performed in young (3 months), middle-aged (6 to 11 months), and aged (26 months) SHR. Fasting plasma glucose was significantly lower in aged SHR than in young SHR. The increase in plasma glucose after glucose administration over fasting level was significantly higher in aged SHR than in middle-aged SHR, but did not differ between young and aged rats. Pancreatic islet size and pancreatic immunoreactive insulin content were similar between young and aged SHR. The present study demonstrated that glucose tolerance did not deteriorate in SHR with aging, while genetic hypertension persisted. This suggests that the persistence of hypertension per se may not affect glucose tolerance in SHR.

Aging↗
PubMed1994

[tRNA identity].

Explore the source record for details and available documents.

Amino Acyl-tRNA Synthetases↗
PubMed1994

Acute hepatic failure with swollen mitochondria and microvesicular fatty degeneration of hepatocytes triggered by free radical initiator.

BACKGROUND: Reye syndrome and acute fatty liver of pregnancy are characterized by acute hepatic failure associated with characteristic pathologic changes of hepatocytes, i.e., microvesicular fatty degeneration with severe mitochondrial swelling. Several animal models of these conditions have been proposed, although none has demonstrated sufficiently similar laboratory and pathologic features. EXPERIMENTAL DESIGN: A single dose of 2,2'-azobis-(2-amidinopropane) dihydrochloride, a free radical initiator, 100 mg/kg of body weight, injected intraperitoneally to BALB/c mice induced a transient decrease in hepatic energy charge, liver mitochondrial respiratory activity, and succinate dehydrogenase activity and a transient increase in blood ammonia level, suggesting hepatic failure. RESULTS: The hepatocytes displayed microvesicular fatty degeneration with severely swollen mitochondria. CONCLUSIONS: This is the first model of acute hepatic failure with microvesicular fatty degeneration of hepatocytes. It suggests a role of free radicals in the pathogenesis of certain types of acute hepatic failure.

Adenine Nucleotides↗
PubMed1993

Recognition nucleotides of Escherichia coli tRNA(Leu) and its elements facilitating discrimination from tRNASer and tRNA(Tyr).

In order to study how Escherichia coli leucyl-tRNA synthetase recognizes tRNA(Leu) and discriminates it from the other two class II tRNAs, tRNA(Ser) and tRNA(Tyr), various mutations were introduced into class II tRNA transcripts. The discriminator base A73, but not the anticodon sequence, was found to serve as a critical recognition element of tRNA(Leu). A base substitution at the invariant nucleotide A14, but not at any of the other nucleotides characteristic of the E. coli tRNA(Leu) isoacceptors among the three class II tRNAs, caused significantly damaged aminoacylation with leucine. A two base-pair deletion in the long variable arm also resulted in no significant decrease of activity. Transplanting the three tertiary elements characteristic of E. coli tRNA(Leu) (i.e. the location of the G18G19 sequence in the D-loop, the A15 U48 base-pair and the stem pairing pattern of the long variable arm) besides the discriminator base change introduced the leucine charging activity in terms of Vmax/Km, up to 0.1 of that for the normal sequence of tRNA(Leu) into both tRNA(Ser) and tRNA(Tyr). These results indicate that A73 and A14 (or its vicinity) are involved in recognition by leucyl-tRNA synthetase, and that several tertiary elements play a significant role in the discrimination of tRNA(Leu) from the other two class II tRNAs.

Base Sequence↗
PubMed1993

Selective induction of an embryonic fibronectin isoform in the rat aorta in vitro.

The temporal changes in the expression of fibronectin and other extracellular matrix genes were studied in rat aortic rings incubated in vitro in a serum-free medium. Changes in all forms of fibronectin mRNA increased progressively during the 24-hour incubation period, although an increase in the alternatively spliced form of fibronectin designated EIIIA was most pronounced. Both collagen and elastin mRNA levels decreased markedly during the 24-hour interval, as did alpha-actin mRNA. The increase in the relative amount of the EIIIA isoform after a 24-hour incubation was also shown using ribonuclease protection assays. In situ hybridization showed the distribution of the induced fibronectin mRNA to be within all cell types, including endothelial cells, medial smooth muscle cells, and adventitial fibroblasts. Localization in the media was not uniform and was clearly identified mainly in clusters of cells distributed throughout the media. The early induction of fibronectin mRNA was inhibited by genistein, implicating tyrosine kinase activation as a causative factor in fibronectin expression. The in vitro changes reported may reflect a phenotypic change in vascular cell types that is both similar to and different from the changes reported in vivo under conditions in which vascular injury and repair occur.

Animals↗
PubMed1993

Closure of ventricular septal rupture caused by acute myocardial infarction using a transaortic balloon catheter.

We report a case of successful transaortic closure of a postinfarction ventricular septal rupture using a Swan-Ganz catheter. The method markedly reduced a left-to-right shunt and the improved hemodynamic condition of the patient, an 81-year-old woman, was maintained for about a week before surgical treatment. Inflation of the balloon with water made the balloon visible via echocardiography and was effective in maintaining inflation and echocardiographic follow-up.

Aged↗
PubMed1993

Discrimination among E. coli tRNAs with a long variable arm.

In E. coli, tRNA(Ser), tRNA(Leu) and tRNA(Tyr) have a long variable arm composed of more than ten nucleotides (class II tRNAs). In order to study how leucyl- and seryl-tRNA synthetase discriminate their cognate tRNA isoacceptors from the other class II tRNAs, kinetic parameters of various mutated class II tRNA transcripts with leucyl- and seryl-tRNA synthetase were determined. Leucyl-tRNA synthetase recognizes A73 and A14 or its vicinity. Seryl-tRNA synthetase recognizes the long variable arm base-nonspecifically. C2-G71 in the acceptor stem functions as a negative identity element against seryl-tRNA synthetase. Difference in the tertiary structure among class II tRNA molecules plays a crucial role in discrimination by these two synthetases.

Acylation↗
PubMed1993

[Recent studies on Ito cells with molecular biology].

By Northern blot analysis of total RNA, extracted from normal human and rat Ito cells, either freshly isolated or in culture, recent studies demonstrated the expression of mRNA for collagen type I, III, IV, fibronectin, laminin, transforming growth factor-beta (TGF-beta), hepatocyte growth factor, nuclear retinoic acid receptor-beta and alpha-smooth m muscle actin. Moreover, Ito cells isolated from experimentally induced fibrotic livers exhibited a marked increase in mRNA for collagen type I, associated with a moderate increase in mRNA of collagen type III and TGF-beta. Although endothelial cells from the same liver also showed moderate increase in mRNA for collagen type I alone, hepatocytes showed no changes. From these results it is concluded that Ito cells are the most important cells in hepatic fibrogenesis.

Animals↗
PubMed1992

Escherichia coli tRNA(Asp) recognition mechanism differing from that of the yeast system.

Various tRNA transcripts were constructed to study the identity elements of Escherichia coli tRNA(Asp). Base substitutions from G34 to U34 at the first position of the anticodon, and from U35 to A35 at the second, severely impaired the aspartate charging activity. The activity was also decreased, but in a more moderate fashion, by base changes at G2-C71, C36 and C38. Identity nucleotides of tRNA(Asp) are distributed in a different fashion between E. coli and yeast, which occur at the second base pair of the acceptor stem, G10-U25 base pair in the D-stem and 3' half of the anticodon loop.

Anticodon↗