Search PubMed⌕ Search

Biomedical subjects

M Taira

Publications and source records attributed to M Taira.

At least 163 records · Page 9Linked to original sources
PubMed1992

Abnormal messenger ribonucleic acid (mRNA) transcribed from a mutant insulin receptor gene in a patient with type A insulin resistance.

In a previous report on a 16-year-old Japanese girl with type A insulin resistance, we found that one allele of the insulin receptor gene was inherited from her mother and contained a 1.2 kilobase pair deletion which removed the 14th exon in the beta subunit. We extended investigation of the proband and found the deletion between two Alu sequences. To determine the effect of the deletion on the level of transcription and the splicing pattern of messenger ribonucleic acid (mRNA), we synthesized the complimentary DNA and used the polymerase chain reaction to amplify the region which included the deleted area. The deletion shifted the reading frame, resulting in a termination codon after amino acid 867 (Glu), thereby producing a truncated insulin receptor without a transmembrane region and cytoplasmic domain. We also sequenced each of 22 exons of the insulin receptor gene but found no mutation in exons of the insulin receptor gene, except for deletion of exon 14 of the maternal allele. Thus, the proband is a heterozygote for a single mutant allele. Abnormal mRNA transcribed from the mutant allele resulted in a decrease in insulin binding.

Adolescent↗
PubMed1992

The LIM domain-containing homeo box gene Xlim-1 is expressed specifically in the organizer region of Xenopus gastrula embryos.

A novel cysteine-rich motif, named LIM, has been identified in the homeo box genes lin-11, Isl-1, and mec-3; the mec-3 and lin-11 genes determine cell lineages in Caenorhabditis elegans. We isolated LIM class homeo box genes from Xenopus laevis that are closely related to lin-11 and mec-3 in the LIM and homeo domains. This paper deals with one of these genes, Xlim-1. Xlim-1 mRNA is found at low abundance in the unfertilized egg, has a major expression phase at the gastrula stage, decreases, and rises again during the tadpole stage. In adult tissues the brain shows the highest abundance, by far, of Xlim-1 mRNA. The maternal and late expression phases of the Xlim-1 gene suggest that it has multiple functions at different stages of the Xenopus life cycle. In the gastrula embryo, Xlim-1 mRNA is localized in the dorsal lip and the dorsal mesoderm, that is, in the region of Spemann's organizer. Explant experiments showed that Xlim-1 mRNA is induced by the mesoderm-inducer activin A and by retinoic acid, which is not a mesoderm inducer but affects patterning during Xenopus embryogenesis; application of activin A and retinoic acid together results in synergistic induction. The structure, inducibility, and localized expression in the organizer of the Xlim-1 gene suggest that it has a role in establishing body pattern during gastrulation.

Activins↗
PubMed1992

Characterization of inorganic fillers in visible-light-cured dental composite resins.

Inorganic fillers in seven visible-light (VL)-cured dental composite resins were examined for their size, composition, phase and content, employing the following analytical instruments. SEM observations indicated that five samples could be classified into the hybrid type while the remaining two belonged to micro-filled and sub-micron types. EDX analyses revealed that five samples contained BaO while others lacked BaO. XRD analyses showed that three were in vitreous phase, two were in the crystalline phase and two were mixtures of both. DTG thermal analyses indicated that the hybrid type composites had the higher inorganic filler content (wt%) than the composites of two other types. In conclusion, wide varieties exist in the inorganic fillers in VL-cured dental composite resins currently utilized.

Aluminum Oxide↗
PubMed1992

Diet-induced atherosclerosis in cynomolgus monkey aorta and regression by the sixth-month observation.

Pathomorphologic analysis was employed to evaluate diet-induced atherosclerosis in cynomolgus monkey aorta and regression by administration of a hypolipidemic agent for six months after the atherogenic ration. Twenty-seven male cynomolgus monkeys were divided into three groups. Group A was fed individually with a high-fat diet containing 0.3% cholesterol under identical conditions for six months. Group B was fed with normal monkey chow for six months after the same atherogenic ration. Group C was fed with normal monkey chow and administered a hypolipidemic agent 1% of 4-[2-(4-isopropylbenzamido)ethoxy] benzonic acid for six months after the same atherogenic ration. Each thoracic and abdominal aorta of animal models was separately analyzed. Lipid composition analysis and esterified cholesterol (CE) in aortic wall, ratio of free cholesterol to phospholipid, surface involvement, and atherosclerotic index after Sudan IV staining were studied for evaluation of progression and regression. The configurations of atherosclerotic involvement were histologically evaluated among each group. These observed lesions, features specific to cynomolgus lesions, mainly consisted of lipid-rich foam cells, lipid debris, and proliferated extracellular matrix. No different lesion composition was noted between the thoracic and abdominal aorta. This may suggest that some local factors play an important role for development of atherosclerosis after the initial event. Group C had remarkable reduction of foam cells and of CE accumulation in both the thoracic and abdominal aortic wall. Accelerated regression in group C as compared with group B was demonstrated both biochemically and pathohistologically. These results suggest that substantial regression of atherosclerosis in both the thoracic and abdominal aorta can be expected. This hypolipidemic agent exerts notable antiatherosclerotic activity, along with a lowering effect on plasma total cholesterol levels.

Animals↗
PubMed1991

Expression of rat phosphoribosylpyrophosphate synthetase subunits I and II in Escherichia coli. Isolation and characterization of the recombinant isoforms.

The 34-kDa subunit of rat liver phosphoribosylpyrophosphate synthetase is a mixture of the two highly homologous isoforms, PRS I and PRS II. Heretofore, it was not possible to separate the two. We now describe isolation and characterization of the recombinant isoforms, named rPRS I and rPRS II. The respective rat cDNAs were inserted into vectors constructed from pKK233-2 by replacing its replication origin with that of pGEM-1 and expressed in Escherichia coli. The rPRS I and rPRS II were purified to apparent homogeneity with specific activities of 33,400 and 46,200 milliunits/mg, respectively; these values were at least 2.5-fold higher than the highest value for the mammalian enzyme so far reported. Both isoforms showed a similar dependency on Pi as an absolute activator. Sulfate partially substituted for Pi. The maximal activities of rPRS I and rPRS II with sulfate were 43 and 7%, respectively, of those seen with Pi. The two isoforms differed in sensitivity to inhibition by ADP and GDP. Inhibition of rPRS I and rPRS II by 0.3 mM ADP was 87 and 54%, respectively, and inhibition by 1 mM GDP was 93 and 24%, respectively. rPRS II was 180-fold more sensitive than rPRS I to heat inactivation at 49 degrees C.

Animals↗
PubMed1991

Defects in insulin binding and receptor kinase in cells from a woman with type A insulin resistance and from her family.

Defects in insulin receptor function lead to impairment of the insulin response. We treated a patient with the typical phenotype of type A syndrome of insulin resistance whose insulin receptor seemed to lack the transmembrane region and cytoplasmic domain. Hyperinsulinaemia and resistance to exogenous insulin were evident, and insulin binding to cells and uptake of 2-deoxyglucose into fibroblasts were greatly decreased. Molecular weight of the alpha-subunit of the insulin receptor was normal, but autophosphorylation and kinase activity were impaired. In the pedigree analysis, defects in insulin binding were also observed in the mother, maternal grandfather and two maternal aunts, corresponding with the abnormality of the insulin receptor gene and mild insulin resistance. In the mother, much the same kinase defects as were seen in the patient became evident. However, no relatives had clinical symptoms similar to those seen in the patient. In the father there was a mild insulin resistance in the glucose clamp study and a borderline impaired glucose tolerance. Although insulin binding to cells was normal in the father, both autophosphorylation and kinase activity were reduced. Our findings suggest that insulin resistance in the patient may be caused by the defects in insulin receptor kinase activity as well as by a reduction in insulin binding activity.

Adolescent↗
PubMed1991

Depression of liver-specific gene expression in regenerating rat liver: a putative cause for liver dysfunction after hepatectomy.

We carried out studies on the expression of liver-specific genes during regeneration of the liver and searched for changes in the expression of oncogenes and housekeeping genes. Albumin and ornithine transcarbamylase genes were the liver-specific genes examined by Northern blot analysis, using total RNAs isolated from residual livers of Sprague-Dawley rats subjected to a 68% partial hepatectomy. The mRNA levels of both genes began to decrease 8 hr after hepatectomy, both reaching the lowest levels at 24 hr, and then recovered to some extent at 48 hr. In contrast, these levels in the housekeeping and growth-related genes were augmented during this period. This would suggest that there is a selective expression of growth-related and housekeeping genes, in preference to liver-specific genes during liver regeneration. The expression of these genes in the regenerating liver was simulated in primary cultured hepatocytes during the dedifferentiation processes. It would appear that the first step in regeneration of the residual liver is dedifferentiation, in which the depression of liver-specific genes may be linked to liver dysfunction following hepatectomy.

Animals↗
PubMed1991

Cutting effectiveness and wear of carbide burs on eight machinable ceramics and bovine dentin.

As a first approach in evaluating the feasibility of industrial machinable ceramics in dentistry, we performed weight-load-cutting tests on eight machinable ceramics and bovine dentin, using #1557 carbide burs driven by an air-turbine handpiece. While the transverse load applied to the bur was cyclically varied between 20 and 80 g, we measured the cutting speed (i.e., the steady-state handpiece speed during cutting) and the cutting volume. The greater the applied load, the more the cutting speed decreased and the cutting volume increased. The degree of this trend, however, differed among the workpieces. When dentin and mica-based glass ceramics were being cut, the cutting speed was moderately reduced, the cutting effectiveness of the bur remained high, and the wear of the bur was small. When other ceramics--such as AIN-based, Si3N4-based, and CaO.SiO2-based ceramics--were being cut, however, the cutting speed was less diminished, and the cutting efficiency of the bur was smaller and decreased rapidly, along with extensive wear of the bur. We speculate that mica-based glass ceramics could be used as the substitute for dentin in the pre-clinical cutting exercise, and that another potential use of machinable ceramics examined might be in the production of future machined dental prostheses.

Animals↗
PubMed1991

Residual monomers (TEGDMA and Bis-GMA) of a set visible-light-cured dental composite resin when immersed in water.

Rods of a visible-light-cured dental composite resin were photo-polymerized and immersed in water at 37 degrees C for 7 days. The residual monomers (TEGDMA and Bis-GMA) trapped in the set composite and those eluted into water were analysed by gas-liquid chromatography. It became evident that minor amounts of the residual monomers dissolved in water, but that most residual monomers remained in the set composite. Extension of the irradiation period contributed to the significant reduction in the residual monomer level and its elution into water.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1991

Refractive-index-adjustable fillers for visible-light-cured dental resin composites: preparation of TiO2-SiO2 glass powder by the sol-gel process.

New fillers have been prepared for visible-light-cured (VL) dental resin composites with the refractive index adjustable to that of the resin phase. These SiO2 glass powders containing TiO2 up to 20 wt% were formed by heating to 1000 degrees C ground gels made from a mixture of Ti[OCH(CH3)2]4 and Si(OC2H5)4. With increasing TiO2 content, the refractive index of the prepared power increased linearly, while the optical transmittance at 467 nm decreased linearly. The experimentally formulated VL-cured resin composites, consisting of (TEGDMA and Bis-GMA) monomer mixture and TiO2-SiO2 glass filler, had greater transmittance when the refractive index of the filler matched that of the monomer mixture, resulting in a greater degree of monomer conversion upon irradiation with VL.

1-Propanol↗
PubMed1991

Complete nucleotide sequence of human phosphoribosyl pyrophosphate synthetase subunit I (PRS I) cDNA and a comparison with human and rat PRPS gene families.

cDNA clones for human phosphoribosyl pyrophosphate synthetase subunit I (PRS I) were isolated from a glioblastoma cell line MGC 1 cDNA library. The longest clone contained 2,075 base pairs (bp) almost covering the 2.3-kb mRNA and the base sequence of the coding region (954 bp) had a 92.0% sequence homology with that of rat PRS I cDNA. The deduced amino acid sequences were identical between human and rat PRS I. This perfect conservation has heretofore not been reported for other enzymes involved in nucleotide metabolism and glycolysis. A comparison with other isoforms of this enzyme, PRS II and PRS III, showed that the human PRS I was 79.9 and 92.2% homologous in the coding sequence and 95.3 and 94.0% in the deduced amino acid sequence to human PRS II and PRS III, respectively. The high value of the synonymous difference between PRS I and PRS II cDNAs places their time of divergence long before that of the radiation of mammals. Based on the evolutionary rate of amino acid substitution, the PRS I and II genes probably diverged about 760 million years ago.

Amino Acid Sequence↗
PubMed1991

Comparison of putative cGMP-binding regions in bovine brain and cardiac cGMP-stimulated phosphodiesterases.

After photolabelling of purified bovine brain particulate cGMP stimulated phosphodiesterase (PDE) with [32P]cGMP, incubation with V8 Endoproteinase Glu-C produced several fragments; most of the [32P] was associated with smaller fragments (approximately 12-14 kDa), and some occasionally with larger fragments (approximately 55-57 kDa). Partial amino acid sequences were determined for the smaller photolabelled fragments and other peptides. On Western immunoblots, affinity-purified antibodies against a synthetic peptide with a sequence matching part of that of the approximately 12-14 kDa photolabelled material reacted with intact PDE and the approximately 12-14 kDa and approximately 55-57 kDa fragments. Several partial cDNA clones encoding the cGMP-stimulated PDE were isolated from a Lambda Zap II bovine brain cDNA library. Deduced amino acid sequence from one cDNA clone, lambda cGS 3-1, as well as the partial sequence of the approximately 12-14 kDa and other fragments, exhibited considerable identity with amino acid residues 311-921 of the cardiac cGMP-stimulated PDE (Trong et al., 1990), including the putative cGMP-binding domain (Charbonneau et al., 1990). These results further define this cGMP-binding domain and suggest that different cGMP-stimulated PDEs will exhibit considerable homology, at least in their cGMP-binding region(s) and catalytic domains.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Chemiluminescent method for continuous monitoring of nitrous acid in ambient air.

A continuous-flow method for measuring atmospheric HNO2 concentration in real time has been developed that uses a chemiluminescent NOx monitor. A Na2CO3 solution strips gaseous HNO2 from the atmosphere by means of pulling an air sample and the solution through a glass coil and mixing continuously with ascorbic acid solution which reduces nitrite to NO. The mixture is led into a gas-liquid separating coil consisting of microporous PTFE tubing. The NO evolved from the separating coil is swept out by a stream of clean air and detected with a chemiluminescent NOx monitor. The technique utilizes a dual flow system and dual channel NOx monitor to correct positive interferences from NO2 and peroxyacetyinitrate (PAN). The concentration of HNO2 is determined by difference between the two measurements. Sensitivity of the method is a function of the ratio of sampling flow rate to carrier gas flow rate, which permits readily a highly sensitive measurement.

Air↗
PubMed1990

A human testis-specific mRNA for phosphoribosylpyrophosphate synthetase that initiates from a non-AUG codon.

Two highly homologous subunits for phosphoribosylpyrophosphate synthetase are encoded by human X-linked genes, PRPS1 and PRPS2 (Taira, M., Kudoh, J., Minoshima, S., Iizasa, T., Shimada, H., Shimizu, Y., Tatibana, M., and Shimizu, N. (1989b) Somat. Cell Mol. Genet. 15, 29-37). These genes are expressed in most tissues, whereas an additional unique mRNA (1.4 kilobases) is present in the testes of rats as well as mice and humans (Taira, M., Iizasa, T., Yamada, K., Shimada, H., and Tatibana, M. (1989a) Biochim. Biophys. Acta 1007, 203-208). In this paper, cDNA cloning revealed that the human testis-specific mRNA was encoded by an autosomal gene, termed PRPS3. RNA blot analysis showed that the expression of this gene began at 4 weeks of age in rats, coinciding with the reported appearance of primary spermatocytes. A cDNA clone of PRPS3 was sequenced and found to encode a predicted product of 317 amino acids which was highly homologous to those of PRPS1 and PRPS2 (94.3% and 91.2% identities, respectively). However, the PRPS3 cDNAs lacked an ATG initiator for translation at the expected position, and instead contained an ACG triplet. In vitro transcription/translation studies, combined with in vitro site-directed mutagenesis experiments, suggested that the ACG codon at this position did serve as a start codon. Analysis of amino-terminal sequence of the radiolabeled PRPS3 product, prepared by in vitro translation, supported the predicted sequence starting with Pro-1, and, in addition, this product was labeled with N-formyl[35S]methionyl-tRNAi. These results suggested that the synthesis of the nascent polypeptide could initiate with methionine at the position corresponding to the ACG codon.

Amino Acid Sequence↗
PubMed1990

Selective activation of testis-specific genes in cultured rat spermatogenic cells.

During mammalian spermatogenesis the isozyme pattern of a glycolytic enzyme, phosphoglycerate kinase (PGK; ATP: 3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3), changes from the somatic-type PGK-1 to the testis-specific PGK-2, and this change has been suggested to involve transcription switch. We have isolated genomic DNA fragments which code for the mouse PGK isozymes and determined the transcription start site of each gene. The results demonstrate that transcriptions of the two PGK genes are initiated at multiple sites under the control of TATA box-lacking promoters. The putative promoter regions of the two genes contain several distinct sequences known as the CCAAT box and the GC box which possibly bind CCAAT-binding proteins and Sp1, respectively. We next developed a culture system in which spermatogenic gene expression is partly reproduced. When spermatogenic cells of 20-day-old rats were cultured, transcripts from PGK-2 and another spermatogenic gene PRPS3 became detectable, while expression of other non-spermatogenic genes did not significantly change during culture. These results suggest that two spermatogenic genes PGK-2 and PRPS3 were activated in culture according to a developmental program of spermatogenesis. Thus, this culture system may be useful for studying the molecular mechanism underlying mammalian spermatogenic gene expression.

Animals↗
PubMed1990

Insulin-resistant diabetes associated with partial deletion of insulin-receptor gene.

The insulin-receptor genes from a 16-year-old girl with type A insulin resistance, who presented with fasting hyperinsulinaemia, acanthosis nigricans, and reduced insulin binding, and from her family were examined. One allele of her insulin-receptor gene inherited from her mother contained a 1.2 kb deletion arising from a recombination between two Alu elements. The deletion removed the 14th exon in the beta subunit and altered the reading frame, to produce a stop codon after aminoacid 867. Pedigree analysis indicated that this mutation alone will not cause diabetes, and the proband is possibly a compound heterozygote. 4 other members of her family were heterozygous for the same mutation; all 4 had a decrease in insulin binding and slight impairment of glucose tolerance. Perhaps the same mutation is an underlying feature of some cases of non-insulin-dependent diabetes mellitus.

Adolescent↗