PubMed Health⌕ Search

Biomedical subjects

S Ejiri

Publications and source records attributed to S Ejiri.

At least 55 records · Page 3Linked to original sources
PubMed1995

Comparison of the effects of intermittent and continuous administration of human parathyroid hormone(1-34) on rat bone.

We compared the effects of synthetic human parathyroid hormone (1-34) (hPTH[1-34]) on rat bones when administered by intermittent injection and by continuous infusion for 4 weeks. Continuous infusion of hPTH(1-34) caused a dose-dependent decrease in the dry weight of the femur and a hyperparathyroidism-like condition in the high-dose group (214 ng/kg/h). In this group, although bone morphology was quite abnormal, the metaphyseal trabecular bone volume increased, whereas the epiphyseal trabecular bone volume tended to decrease, enhancing both bone resorption and formation. The diaphyseal cortical bone of the tibia became markedly porous, and this appeared to be the main cause of the decrease in total bone weight. Conversely, the dry weight of the femur increased in a dose-dependent manner in the intermittent-injection groups. Neither porosity of the cortical bone nor abnormal morphology of the trabecular bone was observed. The volume of the metaphyseal trabecular bone increased while retaining its normal morphology. The epiphyseal trabecular bone formation obviously increased without increase in the number of osteoclasts. In other words, it was postulated that the total weight of bone increased because intermittent injection of hPTH(1-34) increased the trabecular bone volume without loss of the cortical bone volume. These results show that either mode of treatment with hPTH(1-34) continuously accelerated bone formation, whereas the continuous infusion was essential for persistently and markedly enhanced acceleration of bone resorption. It appears that the increase in bone volume with intermittent injection of hPTH(1-34) resulted from the prominent manifestation of its bone-formative action rather than from its bone-resorptive action.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1995

Tapetum-specific expression of the gene for an endo-beta-1,3-glucanase causes male sterility in transgenic tobacco.

A cDNA for a pathogenesis-related endo-beta-1,3-glucanase isolated from soybean, was fused to an anther tapetum-specific promoter (Osg6B promoter) isolated from rice and the resulting chimeric gene was introduced into tobacco. The Osg6B promoter became active in the anther tapetum during formation of tetrads and the tapetal glucanase activity in the transgenic plants caused in a significant reduction in the number of fertile pollen grains. Most of the pollen grains were aberrant in shape, lacked germinal apertures and aggregate of the pollen grains. Granules of beta-1,3-glucan, which have not previously been reported, were often observed to adhere to the surface of the pollen grains. Further observations revealed that the callose wall was almost absent in the pollen tetrads of transgenic plants. In wild-type plants, by contrast, the tetrads were surrounded by callose that was degraded soon after the tetrad stage to release free microspores. Thus, the introduced gene for endo-beta-1,3-endoglucanase under the control of the Osg6B promoter caused digestion of the callose wall at the beginning of the tetrad stage, a time that was just a little earlier than the time at which endogenous glucanase activity normal appears. These results demonstrate that premature dissolution of the callose wall in pollen tetrads causes male sterility and suggest that the time at which tapetally produced glucanase is activate is critical for the normal development of microspores.

Base Sequence↗
PubMed1995

Histological observations of dental tissues using the confocal laser scanning microscope.

To investigate the time course of mineralization in undecalcified dental tissues, calcein- and tetracycline-labeled rat maxillary molar sections were stained with Villanueva bone stain en bloc, embedded in methyl-methacrylate (MMA), ground to 50 microns thickness, and observed by confocal laser scanning microscopy (CLSM). This method allowed observation of dental structures including odontoblasts, pulp cells and periodontal ligament, and dentinal tubules and enamel rods at high resolution; labeled enamel, dentine, and cementum could be observed simultaneously regardless of section thickness. CLSM permitted simultaneous observation of both the components of calcified tissue and the cellular components of dental tissues, and assessment of the mineralization time course of hard tissues labeled by tetracycline or calcein. The technique is useful for both assessing the elements composing dental structure and observing the histological dynamics by which dental structure develops.

Animals↗
PubMed1994

Initiation zone of DNA replication at the aldolase B locus encompasses transcription promoter region.

Aldolase A (AldB) gene is one of the liver-specific genes, which is activated in the fetal stage. As a first step to investigate the functional relationship between transcription and DNA replication, we intended to determine the initiation zone of replication nearest to the AldB gene region. BrdU-labeled nascent DNA was obtained from G1/S arrested hepatoma cells at various times after entering S phase. Hybridization of the newly synthesized, BrdU-labeled DNA with probes corresponding to regions spanning about 26 Kb, revealed that replication zone locates within the AldB gene region. This result, together with the result of hybridization of nascent DNA obtained by alkaline sucrose density-gradient centrifugation, suggested that the initiation zone is located within a more defined region (about 1.0 Kb) containing AldB promoter. In the predicted initiation zone, a purine-rich element which shows high homology to known mammalian origin sequences and other replication components are found. Further, autonomously replicating activity of this initiation zone was examined by DNA transfection. The results showed that the predicted initiation zone confers replication initiation in Cos-1 cells.

Animals↗
PubMed1994

A factor protecting mammalian [75Se]SeCys-tRNA is different from EF-1 alpha.

In Escherichia coli, an elongation factor (EF-Tu-like) specific to SeCys-tRNA, SELB, has been identified; however, a mammalian counterpart of SELB has not been reported to date. We searched for and found this factor in bovine liver extracts using the assay of [75Se]SeCys-tRNA protecting activity against alkaline hydrolysis (SePF activity). We found SePF activity in the protein extracts of the precipitate (microsomal fraction) collected at 150,000 x g from bovine liver. The proteins were separated by Sephacryl S-300 chromatography, and the SePF and EF-1 alpha activities were found in the same fraction, indicating that SePF and EF-1 alpha have the same molecular mass (approximately 50 kDa). We then chromatographed this active fraction using CM-Sephadex C-25 columns. The SePF activity was eluted after the peak of EF-1 alpha activity. This result indicated that this SePF activity was not dependent on EF-1 alpha. In addition to performing these two chromatographies, we investigated pure EF-1 alpha from Bombyx mori but could not detect any SePF activity in B. mori EF-1 alpha. Thus we showed that the SePF activity in bovine liver differs from that of EF-1 alpha in eukaryotes. Therefore the factor protecting [75Se]SeCys-tRNA in bovine liver is not EF-1 alpha and must be a SELB-like factor.

Animals↗
PubMed1994

Structural analysis of the chloroplastic and cytoplasmic aldolase-encoding genes implicated the occurrence of multiple loci in rice.

The genes AldP and AldC-a, encoding the rice chloroplastic (cp) and cytoplasmic (ct) types of aldolase, respectively, were isolated and sequenced, and their transcription start points (tsp) were determined. Organization of the two genes was found to differ greatly; AldP consisted of six exons while AldC-a consisted of two exons. The deduced amino acid (aa) sequence of AldP contained a cp stromal targeting signal, followed by a sequence that matches the experimentally determined N-terminal sequence of mature AldP. The two enzymes share only 55% aa identity. However, rice AldP had about 73% homology with the cp aldolase of spinach. Also, the homology of AldC-a with maize, spinach and Arabidopsis thaliana cytoplasmic aldolases ranged from 70 to 90%. Southern blot analyses indicated that AldP is encoded at a single locus, whereas the gene encoding the ct counterpart is distributed at three loci on the genome. This feature is quite different from those of maize and spinach, in which only one locus was found for the ct aldolase.

Amino Acid Sequence↗
PubMed1994

Interactions among four subunits of elongation factor 1 from rice embryo.

To establish the subunit construction of elongation factor EF-1, interactions among four non-identical subunits of rice embryo EF-1 (alpha, beta, beta', and gamma) were analyzed with polyacrylamide gel electrophoresis. Complexes beta beta', alpha beta, alpha beta', and beta gamma were formed by mixing the two respective subunits. However, no complex was formed between EF-1 beta' and EF-1 gamma. Complexes containing three subunits like alpha beta beta', alpha beta gamma, and beta beta' gamma, were formed by mixing the three respective subunits. EF-1 was reconstructed when each subunit was added in the following order, beta, beta', gamma, and alpha. The affinity of EF-1 alpha for other subunits was as follows, beta beta' gamma > beta beta' > beta not equal to beta'. Likewise, the affinity of EF-1 gamma for other subunits was: beta beta' gamma > beta >> beta'. Phe-tRNA binding activity of the reconstructed EF-1 was about 90% of that of the native EF-1. From these results, we concluded that rice embryo EF-1 is constructed of equimolar amount of four subunits, alpha, beta, beta' and gamma.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1994

Cloning and characterization of the cDNA encoding rice elongation factor 1 beta.

We have cloned and sequenced a cDNA coding for rice elongation factor 1 beta (EF-1 beta). The clone was 1420 bp long and contained an open reading frame coding for 229 amino acids. The overall identity between rice EF-1 beta and rice EF-1 beta' [Matsumoto, S., Oizumi, N., Taira, H. and Ejiri, S. (1992) FEBS Lett. 311, 46-48] is 60% at the amino acid sequence level; a higher percent identical residues (81%) were especially observed in the C-terminal region. Rice EF-1 beta has no conserved phosphorylation site for casein kinase II and no leucine zipper motif, although these motifs are well conserved in EF-1 delta (= beta in plants) subunits of animal EF-1.

Amino Acid Sequence↗
PubMed1994

Histochemical and autoradiographic studies on elcatonin internalization and intracellular movement in osteoclasts.

The binding sites and chronologic localization of elcatonin (eCT) in osteoclasts were examined by autoradiography using [125I]elcatonin (125I-eCT). In addition to the structural changes induced by calcitonin (CT) reported so far, changes were also observed in the structure of Golgi apparatus. These changes continued until 48-72 h after incubation with eCT. Developed silver grains of 125I-eCT were localized into multinucleated osteoclasts and mononuclear cells that were ultrastructurally defined as "preosteoclasts." The silver grains located on plasma membranes of those cells and were then internalized; they accumulated, especially in the Golgi apparatus, and remained for 48-72 h. A few silver grains were also detected in lysosomes and small vesicles. The decrease in the number of silver grains in the Golgi apparatus accompanied the recovery of osteoclast structures--Golgi apparatus and then ruffled borders. These findings suggest that (1) CT especially inhibits the sorting function of Golgi apparatus in osteoclasts, resulting in prolonged retention of CT in this organelle. (2) The CT in Golgi apparatus may keep its activity and cause the prolonged effect of CT on osteoclast activity.

Animals↗
PubMed1994

Molecular characterization of rice genes specifically expressed in the anther tapetum.

In situ localization of mRNA was carried out on two cDNAs (Osc4 and Osc6) that had been isolated from rice anthers at the microspore stage. The mRNA corresponding to each cDNA was shown to be localized only in the tapetal cells of the rice immature anthers, but not in the microspores or the mature pollen. The corresponding genomic clone, Osg6B, was isolated, and its 5'-upstream region was found to regulate beta-glucuronidase expression in the tapetum of transgenic tobacco. A set of 5' deletions was also generated and a 1095 bp 5' region was revealed to be necessary for activation of the Osg6B promoter in transgenic tobacco.

Base Sequence↗
PubMed1994

Ultrastructure of human skin by a rapid freezing technique: structural preservation and antigenicity.

To investigate the natural fine structure of skin, human skin biopsies were studied by electron microscopy and immunoelectron microscopy using rapid freezing and freeze-substitution techniques. Well-preserved structures were observed within a depth of 20 microns from the slammed surface of the samples. Epidermal cells were always closely located with very narrow intercellular spaces. Keratin filaments were distributed densely and homogeneously without forming bundles in the cytoplasm of epidermal keratinocytes. Langerhans cell granules were composed of a flat vesicular portion and an oval rod portion. The most striking finding was in the dermal-epidermal junction, where the lamina densa was present but no lamina lucida was observed. Further, by immunoelectron microscopy with anti-keratin monoclonal antibody, the 20-microns-deep part of the samples revealed the most significant staining. These findings indicate that the ultrastructure of routinely processed skin samples may be modified during the procedure for conventional chemical fixation and dehydration and that the ultrastructurally most preserved specimens, reflecting the conditions close to natural in vivo structures of the skin, can be obtained by the techniques described in this paper.

Adolescent↗
PubMed1993

Ubiquitous factors that interact simultaneously with two distinct cis-elements on the rat aldolase B gene promoter.

The proximal promoter region (nucleotide -202 to -1) of the rat aldolase B gene confers liver-specific transcription, and contains three indispensable protein-binding sites (site A, site B and site C). Site A binds HNF-1 and HNF-3, and site B binds NF-Y and a CCAAT-binding factor AlF-B (Tsutsumi et al. (1989) Mol. Cell. Biol. 9, 4923-4931; Raymondjean et al. (1991) Nucleic Acids Res. 19, 6145-6153), trans-acting factors that interact with site C, however, have not been well characterized. In this study, we identified specific factors that bind site C by two-dimensional gel electrophoretic analyses. The factors interacted with two distinct cis-elements; site C and site B. This observation, together with the fact that site C contains a C/EBP binding motif, implied that the site C-binding factors are members of C/EBP family. However, analyses of their binding characteristics, their relative molecular masses, and their distribution in different cell types showed that the site C binding factors are different from known members of C/EBP family.

Albumins↗
PubMed1993

Analysis of phosphorylation of wheat elongation factor 1 beta and beta' by casein kinase II.

The purified casein kinase II (CK II) from Arabidopsis thaliana phosphorylates wheat elongation factor 1 beta (EF-1 beta), but not elongation factor 1 beta' (EF-1 beta'), which lacks a serine residue in the conserved phosphorylation site. Both EF-1 beta and beta' subunits, with similar functions, seem to undergo different regulation despite the partial amino acid sequence of EF-1 beta being similar to that of EF-1 beta'.

Amino Acid Sequence↗
PubMed1992

Cloning and sequencing of the cDNA encoding rice elongation factor 1 beta'.

A cDNA clone coding for rice elongation factor 1 beta' (EF-1 beta') was isolated from a rice anther cDNA library. The clone, named RB', was 980 bp long and contained a single open reading frame coding for 223 amino acids; the first 31 amino acids, except for the first methionine, which is absent in the mature protein, are identical to those of the purified protein determined with a protein sequencer. The amino acid sequence of rice EF-1 beta' shows homology to the C-terminal half of Artemia salina EF-1 beta (59%) and human EF-1 beta (63%), but might not have a phosphorylation site for casein kinase II which has been conserved in Artemia saline EF-1 beta and EF-1 delta, human EF-1 beta and silkworm EF-1 beta'.

Amino Acid Sequence↗