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Biomedical subjects

T Nagata

Publications and source records attributed to T Nagata.

At least 379 records · Page 21Linked to original sources
PubMed1993

[The effect of intraocular lens (IOL) length and design on anterior chamber depth under contraction and relaxation of the ciliary muscle].

We compared the effect of intraocular lens (IOL) length and its design on the anterior chamber depth (ACD) change during contraction and relaxation of the ciliary muscle. We performed phacoemulsification or extra capsular cataract extraction using continuous circular capsulorhexis on 100 eyes, and implanted in 23 eyes a short one-piece IOL, in 22 eyes a short three-piece IOL, in 25 eyes a long one-piece IOL, and in 30 eyes a long three-piece IOL. All IOLs were fixed in the capsular bag. ACD changes after administration of 2% pilocarpine and 1% cyclopentolate were measured with a pachymeter between 3 and 6 months postoperatively. The compatibility of the IOLs with ciliary muscle contraction and relaxation was, in descending order, the short one-piece IOL, the short three-piece IOL, the long one-piece IOL, and the long three-piece IOL. The results indicated that short IOLs are more physiologically fixed in the capsular bag, with less stress on the zonules of Zinn.

Aged↗
PubMed1993

Observation on incorporation of 3H-taurine in mouse skeletal muscle cells by light and electron microscopic radioautography.

Taurine, one of the sulfur-containing amino acids, exist abundantly in the skeletal muscle tissues. The physiological function and ultrastructural cellular localization of taurine in the skeletal muscle cells are not clear. In this report, two experiments by radioautography were made to elucidate intracellular localization of this amino acid in the skeletal muscle cells. First, muscle tissue pieces obtained from normal and muscular dystrophy mice were cultured in a medium containing 3H-taurine and radioautographed. The number of silver grains appeared on muscle cells increased depending on the duration of the incubation time. Secondly, 3H-taurine was injected intraperitonealy in normal and muscular dystrophy mice. Then muscle specimens were fixed by two fixative procedures, one by a chemical fixation with glutaraldehyde and osmium tetroxide and another by cryo-fixation. Silver grains appeared over muscle cells prepared with both procedures. Silver grains were localized on myofilaments, sarcoplasmic membranes, sarcoplasmic reticulum, mitochondria, endothelial cells of blood capillaries and the cells of perineural sheath, but did not appear on Golgi apparatus, nuclei of muscle cells or adipose cells by any procedures. No difference in localization of silver grains was observed between normal and muscular dystrophy mice.

Actin Cytoskeleton↗
PubMed1993

Light microscopic radioautographic study on DNA synthesis in aging mice corneas.

The morphological change and DNA synthesis of the aging mice corneal cells were investigated by light microscopic radioautography after injection of tritiated thymidine. The result showed that the incorporation of tritiated thymidine in corneal cells changed with aging. The sites of tritiated thymidine incorporation were located in the epithelium from postnatal day 19 to 1 year after birth, in the stroma and endothelium from prenatal day 19 to postnatal day 8 only. The labeling index in the epithelial cells reached its highest value at 1 month after birth. Labelled stromal and endothelial cells reached their peaks simultaneously on the third day after birth and disappeared completely from postnatal 1 month onwards. The thickness of the cornea increased obviously at one month and there were no notable morphological change thereafter. Our investigation provides for the first time a systematic study on the age-related changes of DNA synthesis and construction in the aging mice corneas.

Aging↗
PubMed1993

[Clinical studies on ceftriaxone in respiratory tract infections. CTRX Study Group].

We report that the results of clinical studies on ceftriaxone (CTRX) in respiratory tract infections (RTIs). Clinical efficacies and side effects of CTRX were as follows; 1. Clinical efficacies of CTRX in a total of 61 cases with RTIs were excellent in 11 cases, good in 23, fair in 11, poor in 12 and unknown in 4. Thus the overall clinical efficacy rate was 59.6%. In cases of patients with lung cancers, the efficacy rate was 42.9%. 2. Clinical efficacy rates with once daily dosage were 50.0% with a dose level of 1 g CTRX and 54.8% with that of 2 g CTRX. 3. Side effects were observed in 2 cases (3.1%) and laboratory abnormalities were observed in 1 case (1.6%). They were not serious, however. These data suggest that CTRX is one of the useful cephalosporins in treatment of RTIs.

Adult↗
PubMed1993

Postnatal development and aging of esophageal epithelium in mouse: a light and electron microscopic radioautographic study.

DNA synthesis and fine structure of the esophageal epithelium of ddY mouse in different age groups, from neonatal to senescent, were investigated by light and electron microscopic radioautography after 3H-thymidine labeling in vitro. At 1-3 days after birth, the esophagus was lined with two cell types, ciliated and nonciliated cells. From 1 week on, ciliated cells could not be found. At 2 weeks, the superficial cells still possessed nuclei and short microvilli on the apical plasma membranes. From 1 month, the superficial cells became keratinized and the microvilli on the apical plasma membrane disappeared. With aging of the mice, the epithelia became markedly thick. These results show that disappearance of ciliated cells, keratinization of superficial cells and increase of the thickness are the main changes in structure of mouse esophageal epithelium from neonatal to senescent ages. By light microscopic radioautography, labelled cells were almost confined in the basal layer, regardless of the aging stages. The highest labeling index was recorded at 1 day after birth, then decreased with age. By electron microscopic radioautography, silver grains indicating DNA synthesis were observed in nuclei. As compared with those of unlabelled cells in the basal layer, the nuclei and nucleoli of labelled cells were larger, with fewer cell organelles. The present study provides, for the first time, the basic quantitative data regarding cell proliferation of mouse esophageal epithelium from neonatal to senescent stage.

Aging↗
PubMed1993

Effect of dehydroproline as a collagen synthetic inhibitor in paraquat-induced pulmonary fibrosis in beagle dogs.

To investigate the effect of 3,4-DL-dehydroproline (DHP) on paraquat (PQ)-induced pulmonary fibrosis in beagle dogs, 25 beagles without distinction of sex were allocated at random into 2 groups; 17 dogs were PQ-dosed and 8 were saline-dosed. The 17 dogs were given 1 mg PQ/kg/d sc for 7-11 d; 14 of the 17 had decreased body weight on day 11 and were selected, 2 of which were determined at random and necropsied. The remaining 12 dogs were randomly divided into 2 groups of 6 dogs each (DHP-treated or saline-treated). They received either 25 mg DHP/kg/d sc or saline for 14 d and were sacrificed for measurement of lung lipid peroxide and lung hydroxyproline (Hyp) concentrations on day 25 or 180 after the PQ administrations started. Two of the 17 dogs (11.8%) given 1 mg PQ/kg/d sc died on days 9 and 11 of the administration. One dog (5.9%) had no signs of PQ toxicity including no decrease in body weight. The remaining 14 dogs (82.4%) had decreased body weight until day 11 of the PQ administrations. No significant differences in erythrocyte superoxide dismutase, blood catalase and serum-lipid peroxide occurred from the PQ dosing; however, lung lipid peroxide increased 4-fold. On day 180 the lung lipid peroxide of the PQ + saline treated group was still 4-times elevated, while the PQ + DHP treated group had about 1/2 that value. Lung Hyp concentrations in the PQ dosed dogs were significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Radioautographic study on 3H-thymidine incorporation at different stages of muscle development in aging mice.

The DNA synthesis of mouse intercostal muscle from the 13th prenatal day through postnatal 24 months has been studied by light microscopic radioautography after the injection of 3H-thymidine. Chronological changes of labeling indices showed the highest value at E13, decreased gradually and reached almost 0% at 3 months after birth. We classified the embryonic muscle development into five stages, and the LI at stage I was the highest, the LI at stage II was significantly lower than that at stage I, the LI at stage IV was significantly higher than that at stage II, and the LI at stage V was significantly lower than that at stage IV. These changes accorded well with the primary and secondary myotube formation.

Aging↗
PubMed1992

Clonal dental pulp cells (RDP4-1, RPC-C2A) synthesize and secrete osteopontin (SPP1, 2ar).

Dental pulp cells play an important role in maintaining dental mineralized tissue throughout life. Supplementary mineralization such as reparative dentin and pulp stone frequently occurs after primary dentin formation. Dental pulp cells are thought to be closely associated with such mineralization. We found that clonal rat dental pulp cells, RDP4-1 and RPC-C2A, produce and secrete osteopontin, but do not synthesize phosphophoryn which is a major noncollagenous protein found in dentin. The dental pulp osteopontin was highly phosphorylated and identified by thrombin susceptibility and immunoprecipitation with osteopontin/2ar antibody. Osteopontin synthesis markedly increased by 12-O-tetradecanoylphorbol-13-acetate (TPA) as observed in many osteoblastic cells. This study indicates that these cells can produce osteopontin as a major phosphoprotein and suggests that the synthesis of osteopontin could be used as a characteristic marker of dental pulp cells.

Animals↗
PubMed1992

Systematic sequencing of the Escherichia coli genome: analysis of the 0-2.4 min region.

A contiguous 111,402-nucleotide sequence corresponding to the 0 to 2.4 min region of the E. coli chromosome was determined as a first step to complete structural analysis of the genome. The resulting sequence was used to predict open reading frames and to search for sequence similarity against the PIR protein database. A number of novel genes were found whose predicted protein sequences showed significant homology with known proteins from various organisms, including several clusters of genes similar to those involved in fatty acid metabolism in bacteria (e.g., betT, baiF) and higher organisms, iron transport (sfuA, B, C) in Serratia marcescens, and symbiotic nitrogen fixation or electron transport (fixA, B, C, X) in Azorhizobium caulinodans. In addition, several genes and IS elements that had been mapped but not sequenced (e.g., leuA, B, C, D) were identified. We estimate that about 90 genes are represented in this region of the chromosome with little spacer.

Bacterial Proteins↗
PubMed1992

Retinoic acid-dependent transactivation of major histocompatibility complex class I promoters by the nuclear hormone receptor H-2RIIBP in undifferentiated embryonal carcinoma cells.

H-2RIIBP is a member of the nuclear hormone receptor superfamily that binds to the region II enhancer of major histocompatibility complex (MHC) class I genes. The binding occurs through the GG(T/A)CA motif present also in many other genes. The role of H-2RIIBP in developmental regulation of MHC class I genes has been studied in undifferentiated N-Tera2 embryonal carcinoma cells by transient cotransfection of an expressible H-2RIIBP plasmid and a chloramphenicol acetyltransferase reporter gene linked to the MHC class I promoter. Transfection of the expression plasmid led to production of H-2RIIBP transcripts and enhanced MHC class I promoter activity in cells that were treated with retinoic acid but not yet differentiated. Retinoic acid concentrations required for transactivation overlapped with those capable of inducing morphological differentiation and expression of endogenous MHC class I genes in these cells. This enhancement was mediated by region II, as a heterologous thymidine kinase promoter driven by region II also served as a target for H-2RIIBP transactivation. Deletion of the bulk of the DNA-binding domain or the ligand-binding domain of H-2RIIBP, but not of the N-terminal domain, abolished transactivation, indicating that the former two domains are critical for the enhancement. Moreover, H-2RIIBP transactivation exhibited a strict cell-type restriction. As observed in other cell lines, N-Tera2 cells that had undergone differentiation failed to elicit transactivation, suggesting that H-2RIIBP acts in concert with a cofactor expressed in undifferentiated N-Tera2 cells that requires retinoic acid for its function. These results suggest that H-2RIIBP can function as a developmentally specific transcription factor for MHC class I genes.

Base Sequence↗
PubMed1992

The role of 5'-methylthioadenosine on rat calvaria cell differentiation.

The role of 5'-methylthioadenosine (MTA), formed during the process of polyamine biosynthesis, on differentiation of osteoprogenitor cells was assessed by its effects on alkaline phosphatase (ALP) activity, bone nodule formation and osteopontin contents of cultured rat calvaria (RC) cells. These three markers were stimulated by exogenous MTA and were depressed by 5'-difluoromethylthioadenosine (DFMTA), a synthetic inhibitor of MTA phosphorylase, which cleaves MTA to adenine and 5-methylthioribose-1-phosphate. 5-Methylthioribose and 2-keto-4-methylthiobutyrate, metabolites of 5-methylthioribose-1-phosphate, had no effects on ALP activity and bone nodule formation in the presence or absence of DFMTA. On the other hand, adenine enhanced ALP activity, bone nodule formation and osteopontin contents in mineralized nodules and also partially reversed DFMTA-induced inhibition of these three markers. MTA, its metabolites and DFMTA did not affect the growth of RC cells under these culture conditions. These results suggest that adenine formed from MTA is important in the differentiation of RC cells.

Adenine↗
PubMed1992

parB: an auxin-regulated gene encoding glutathione S-transferase.

We have isolated an auxin-regulated cDNA, parB, from the early stage of cultured tobacco mesophyll protoplasts. The expression of parB was observed during transition from G0 to the S phase of tobacco mesophyll protoplasts cultured in vitro. The predicted amino acid sequence of parB cDNA has 213 amino acid residues with a relative molecular weight of 23,965. Nucleotide sequence analysis revealed that parB cDNA has homology to glutathione S-transferase (GST; RX:glutathione R-transferase, EC 2.5.1.18) from several sources including plant and animal cells. When we introduced expression vector pKK233-2, which retains parB cDNA, into Escherichia coli, we could detect GST activity in the parB gene product. Accordingly a significant increase of GST activity was detected in the tobacco mesophyll protoplasts cultured in the presence of 2,4-dichlorophenoxyacetic acid. This is an example in which the function of auxin-regulated gene product is shown to be ascribed to a specific enzymatic activity. As GST, and its substrate glutathione, are shown to be related to cell proliferation as well as detoxification of xenobiotics in plant and animal cells, the role of parB is discussed in relation to the induction of proliferative activity in differentiated and nondividing mesophyll protoplasts of tobacco.

Amino Acid Sequence↗
PubMed1992

H-2RIIBP (RXR beta) heterodimerization provides a mechanism for combinatorial diversity in the regulation of retinoic acid and thyroid hormone responsive genes.

H-2RIIBP (RXR beta) is a member of the nuclear hormone receptor superfamily that activates transcription of MHC class I genes in response to retinoic acid (RA). Using chemical cross-linking, co-immunoprecipitation, gel mobility shift and streptavidin-biotin DNA precipitation assays, we show that H-2RIIBP formed heterodimers with thyroid hormone (T3) and RA receptors (T3R alpha and RAR alpha). H-2RIIBP heterodimer formation required a conserved sub-domain of its C-terminal region, occurred independently of target DNA and was much more efficient than either T3R alpha/RAR alpha heterodimer or H-2RIIBP homodimer formation. Heterodimers displayed enhanced binding to target DNA elements and contacted DNA in a manner distinct from that of homodimers. A functional role for heterodimers in vivo was demonstrated by synergistic enhancement of MHC class I transcription following co-transfection of H-2RIIBP with T3R alpha or RAR alpha. We provide biochemical evidence that H-2RIIBP formed heterodimers with several naturally occurring nuclear proteins. The results suggest that H-2RIIBP, by virtue of its ability to heterodimerize, enhances combinatorial diversity and versatility in gene regulation mediated by nuclear hormone receptors.

Amino Acid Sequence↗
PubMed1992

Temporal studies on the tissue compartmentalization of bone sialoprotein (BSP), osteopontin (OPN), and SPARC protein during bone formation in vitro.

To study the role of noncollagenous proteins in bone formation, the synthesis and tissue distribution of BSP (bone sialoprotein), OPN (osteopontin) and SPARC (secreted protein acidic and rich in cysteine) were analyzed using pulse-chase and continuous labeling protocols during bone formation by cultures of rat calvarial cells. Following a 1 h labeling period with [35S]methionine or [35SO4], radiolabeled BSP was rapidly lost from the cells and appeared transiently in the culture medium and in a 4 M GuHCl extract (G1) of the mineralized tissue. Coinciding with the loss of BSP from these compartments, radiolabeled BSP increased in demineralizing, 0.5 M EDTA extracts (E) of the bone, in a subsequent GuHCl extract (G2), and in a bacterial collagenase digest (CD fraction) of the extracted tissue, over a 24 h chase period. In comparison, the 55 kDa form of OPN, with a small amount of the 44 kDa OPN, was secreted almost entirely into the culture medium. Most of the 44 kDa OPN, together with some 55 kDa OPN, accumulated rapidly in the E extract but could not be detected in either G extract or in the CD fraction. SPARC appeared transiently in the G1 extract, but was otherwise quantitatively secreted into the culture medium from where it was lost by complexing and/or degradation. When cultures were continuously labeled over a 12 day period with [35S]methionine, radiolabeled BSP and 44 kDa OPN accumulated in the E extract together with a small amount of SPARC. Some radiolabeled BSP also accumulated in the G2 extract. From the relative incorporation of [35SO4] over the same time period, a time-dependent loss in sulphate from the BSP was evident. Using a 24 h pulse-labeling protocol, the amount of radiolabeled BSP and OPN in the E extract and the BSP in the G2 extract were not altered significantly over a 12-day chase period. These studies demonstrate that the 44 kDa OPN and most of the BSP are rapidly bound to the hydroxyapatite crystals where they may regulate crystal formation and growth during bone formation. Some BSP is deposited in the osteoid and appears to become masked by the formation of hydroxyapatite, indicating a potential role for this protein in epitactic nucleation of hydroxyapatite crystal formation.

Animals↗
PubMed1992

Transcription in vivo within the replication origin of the Escherichia coli chromosome: a mechanism for activating initiation of replication.

Within the replication origin, oriC, of the Escherichia coli chromosome, novel in vivo transcripts were detected which proceeded rightward and whose production was activated by DnaA protein. In contrast, DnaA protein repressed the previously described ori-L leftward transcription. The former should introduce negative supercoiling, and the latter positive supercoiling, into the 13-mers. The effects of transcription on the initiation of replication were also investigated by making constructs with promoters placed near oriC. Transcription was found to enhance the origin activity only when it was oriented in such a way as to introduce negative supercoiling into the 13-mers. From these results, we propose that transcription within oriC regulates replication initiation by altering the topology of the 13-mer region.

Base Sequence↗
PubMed1992

The replication origin of proplastid DNA in cultured cells of tobacco.

When tobacco suspension culture line BY2 cells in stationary phase are transferred into fresh medium, replication of proplastid DNA proceeds for 24 h in the absence of nuclear DNA replication. Replicative intermediates of the proplastid DNA concentrated by benzoylated, naphthoylated DEAE cellulose chromatography, were radioactively labelled and hybridized to several sets of restriction endonuclease fragments of tobacco chloroplast DNA. The intermediates hybridized preferentially to restriction fragments in the two large inverted repeats. Mapping of D-loops and of restriction fragment lengths by electron microscopy permitted the localization of the replication origin, which was close to the 23S rRNA gene in the inverted repeats. The replication origins in both segments of the inverted repeat in tobacco proplastid DNA were active in vivo.

Autoradiography↗
PubMed1992

Actions of parathyroid hormone on cultured human dental pulp cells.

The responsiveness of human dental pulp (HDP) cells to parathyroid hormone (PTH) was investigated by measuring their cyclic AMP (cAMP) content, DNA synthesis, alkaline phosphatase activity, collagen synthesis, and glycosaminoglycan (GAG) synthesis. PTH dose-dependently increased the intracellular cAMP 1 min after the addition of PTH. Confluent HDP cells on day 14 expressed a high level of cAMP production after addition of 3 units/ml PTH. The hormone did not affect DNA synthesis by HDP cells. Alkaline phosphatase activity was suppressed by PTH to 81% of control (p < 0.01), and addition of dibutyryl cAMP to the medium mimicked the effect of PTH (79% of control, p < 0.01). The hormone inhibited collagen synthesis (15% decrease of [3H] proline incorporation, p < 0.01), and stimulated non-collagen protein synthesis (10% increase, p < 0.05). The increase of non-collagen protein by PTH was in accordance with the enhancement of GAG synthesis (17% increase of [35S]sulfate incorporation, p < 0.01). Dibutyryl cAMP caused further increase of GAG synthesis, to 155% of control (p < 0.01). Observations of the radiolabeled proteins on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis after metabolic labeling with [14C]proline and [35S]sulfate revealed a similar tendency to the quantitative determinations in which PTH inhibited collagen synthesis and stimulated GAG synthesis. These findings suggest that HDP cells have some osteoblastic characteristics in terms of PTH responsiveness, and that this culture system is a useful model for studies of human dental pulp.

Adolescent↗