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Biomedical subjects

M Imagawa

Publications and source records attributed to M Imagawa.

At least 127 records · Page 7Linked to original sources
PubMed1990

Characterization of metallothionein cDNAs induced by cadmium in the nematode Caenorhabditis elegans.

cDNAs of metallothioneins (MTs) in the nematode Caenorhabditis elegans were characterized. The MT-II clone encodes 62 amino acid residues and the predicted Mr is 6462. The MT-I clone contains an additional 12 residues at the C-terminal end, and the predicted Mr is 7959. There is a considerable similarity between MT-I and MT-II. Both of these proteins are cysteine-rich and, with a few exceptions, show a good alignment of cysteine residues. No obvious sequence relationship in the coding region was discernible between C. elegans MTs and mammalian MTs, aside from Cys-Cys, Cys-Xaa-Cys, and Cys-Xaa-Xaa-Xaa-Cys segments. However, 3'-untranslated region of cDNAs of C. elegans MT-I and -II have some consensus sequences found in mammalian MT cDNAs, suggesting that these regions may have some roles in the regulation of MT-gene expression.

Amino Acid Sequence↗
PubMed1990

Functional cooperativity between two TPA responsive elements in undifferentiated F9 embryonic stem cells.

We have recently identified an enhancer, termed GPEI, in the 5'-flanking region of the rat glutathione transferase P gene, that is composed of two imperfect TPA (phorbol 12-O-tetradecanoate 13-acetate) responsive elements (TREs). Unlike other TRE-containing enhancers, GPEI exhibits a strong transcriptional enhancing activity in F9 embryonic stem cells. Mutational analyses have revealed that the high activity of GPEI is mediated by two imperfect TREs. Each TRE-like sequence has no activity by itself but acts synergistically to form a strong enhancer which is active even in the very low level of AP-1 activity in F9 cells. Furthermore, we show that synthetic DNAs containing two perfect TREs in certain arrangements have strong transcriptional enhancing activities in F9 cells and the activity is greatly influenced by the relative orientation and the distance of two TREs.

Animals↗
PubMed1990

Rapid background reduction of circulating sodium iodide I 125-labelled Pisum sativum agglutinin used as a tumor-imaging radiopharmaceutical by the chemically galactosylated antibody.

Influence on the clearance of background radioactivity from the blood was studied by using a chemically galactosylated antibody to the radiopharmaceutical. Sodium iodide I 125-labelled Pisum sativum agglutinin (125I-PSA) was used as the model tumor-imaging radiopharmaceutical in this series of experiments. Rabbit (anti-PSA) immunoglobulin G (IgG) was chemically galactosylated with varying amounts of cyanomethylgalactose. Galactose concentration ranged from 11 to 17 mol/mol protein. Antibody activity was not affected by chemical galactosylation under the experimental conditions used. Blood clearance of the galactosylated anti-PSA (GAP) in normal mice was enhanced to varying degrees, depending on the degree of galactosylation; similarly, liver uptake was increased with the degree of galactosylation. Following injection of 125I-PSA in normal mice, the lectin was rapidly removed from the blood by subsequent injection of GAP. Increased hepatic uptake of the complex (lectin-galactosylated antibody) via protein-carbohydrate recognition caused the pronounced decrease in the 125I-PSA blood level. The effective time for 125I-PSA removal was as short as 15 min. The potency was dependent on the degree of galactosylation of the antibody. In sarcoma 180 (S-180) tumor-bearing mice, the capacity for blood clearance of 125I-PSA was also positively correlated to the degree of galactosylation. Moreover, the variation in the delivered dose ratio of antibody to lectin proved to lead to a further increase in background clearance. As a result, especially the tumor:blood ratio was significantly improved by a single administration of chemically galactosylated antibody, as compared with the value measured in the presence of unmodified antibody. These initial studies suggest that administration of GAP may improve nuclear imaging with radiopharmaceuticals.

Animals↗
PubMed1990

Renal tissue and urinary kallikrein activity in two-kidney, one-clip hypertensive rats.

Renal tissue and urinary kallikrein activity were studied to assess the role of the renal kallikrein-kinin system in two-kidney, one-clip hypertensive rats. Body weight, urine volume, systolic blood pressure and urinary kallikrein activity were measured in 11 hypertensive rats and 6 normotensive rats 1, 4, 8 and 12 weeks after clipping or sham operation. The hypertensive rats used in the present study had systolic blood pressures of over 180 mm Hg 12 weeks after the operation and presented polyuria with a reduction in weight gain, which placed them in the malignant hypertension category. Urinary kallikrein activity in hypertensive rats significantly decreased from 21.7 +/- 13.3 nkat/day at 1 week to 11.6 +/- 5.5 nkat/day at 12 weeks after clipping (p less than 0.05), while urinary kallikrein activity in normotensive rats significantly increased from 23.6 +/- 8.9 nkat/day at 1 week to 43.7 +/- 16.2 nkat/day at 4 weeks after the sham operation. Significant differences were observed in urinary kallikrein activity between hypertensive rats and normotensive rats 4 and 12 weeks after the operation (p less than 0.05). Renal tissue kallikrein activity from bilaterally nephrectomized kidneys was investigated 12 weeks after the operation. No significant difference in tissue kallikrein activity was found between the two kidneys of the hypertensive rats. However, tissue kallikrein activity was significantly lower in the contralateral kidney of hypertensive rats as compared to the same kidney of normotensive rats (2.13 +/- 0.73 nkat/g in hypertensive rats vs. 3.05 +/- 0.69 nkat/g in normotensive rats, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Mechanism of specific expression of glutathione transferase P gene during hepatocarcinogenesis.

The mechanism of specific expression of glutathione transferase P gene during hepatocarcinogenesis of the rat has been investigated by cloning the gene and determining the upstream regulatory sequences. Two enhancers and a silencer are located within 3 kb upstream of the promoter. The stronger enhancer designated GPEI has two TPA (12-O-tetradecanoyl phorbol 13-acetate)-response element (TRE)-like sequences arranged in a palindrome at a 3 base pairs spacing. This special combination was found to form a very strong enhancer which could act efficiently even in F9 cells where the collagenase enhancer with a singlet TRE cannot work due to the low c-jun content. Whether this structure is operating with a very low concentration of c-jun/c-fos heterodimer or with any other proteins remains to be determined. These findings suggest that new and more efficient enhancers evolve by a combination of basic enhancer elements. The silencer region consists of several sequences that can bind specific protein(s) and works cooperatively.

Animals↗
PubMed1990

Biochemical and immunochemical characterization of Caenorhabditis elegans metallothioneins I and II induced by cadmium.

Metallothioneins in Caenorhabditis elegans (CeMT-I and II) were purified by the combination of gel filtration, ion-exchange chromatography, and high-performance liquid chromatography. Amino acid compositions and amino-terminal sequences of CeMT-I and II were slightly different from those of vertebrate MTs previously reported, although cysteine residue contents were relatively high. Enzyme immunoassay using anti-CeMT-II antibody showed the difference of antigenicity to rat MT-I and II and even to CeMT-I. Immunohistochemical staining revealed the existence of CeMT-II in the intestine and the eggs, suggesting the role of MT in detoxification and homeostasis of heavy metals.

Amino Acid Sequence↗
PubMed1989

Structural and functional analysis of an enhancer GPEI having a phorbol 12-O-tetradecanoate 13-acetate responsive element-like sequence found in the rat glutathione transferase P gene.

We have recently identified a typical enhancer, termed GPEI, located about 2.5 kilobases upstream from the transcription initiation site of the rat glutathione transferase P gene. Analyses of 5' and 3' deletion mutants revealed that the cis-acting sequence of GPEI contained the phorbol 12-O-tetradecanoate 13-acetate responsive element (TRE)-like sequence in it. For the maximal activity, however, GPEI required an adjacent upstream sequence of about 19 base pairs in addition to the TRE-like sequence. With the DNA binding gel-shift assay, we could detect protein(s) that specifically binds to the TRE-like sequence of GPEI fragment, which was possibly c-jun.c-fos complex or a similar protein complex. The sequence immediately upstream of the TRE-like sequence did not have any activity by itself, but augmented the latter activity by about 5-fold.

Animals↗
PubMed1989

Enhancement of clearance of plant lectins as radiopharmaceuticals by chemically glycosylated antilectin antibody.

The influence of chemical glycosylation on clearance of plant lectins, employed as radiopharmaceuticals, was assessed. Controlled chemical modification of the antibody to concanavalia ensiformis agglutinin did not affect its immunologic activity, but led to rapid clearance from circulation. In tumor-bearing mice, notable increases of selected tumor/non tumor ratios even after only 1 h of presence of the galactosylated antibody to the lectin in circulation were observed. Similarly, galactosylated antibody to pisum sativum agglutinin caused significant increases of tumor/non tumor ratios.

Animals↗
PubMed1988

Identification of a nuclear factor that binds to a conserved sequence of the I-A beta gene.

Human and murine class II genes of the MHC show a striking homology 50 to 120 bp upstream of the transcription start site. This area is composed of two conserved sequences (a 13-mer and an 8-mer separated by 19 to 20 bp). Recently, these conserved sequences have been identified as cis-acting transcriptional regulatory elements. We have sought nuclear factors that bind specifically to an upstream fragment (-245 to +75 bp) of the murine I-A beta chain gene that contains the conserved sequences by application of a modified gel electrophoresis DNA binding assay. We report here the identification of a nuclear factor whose binding site overlaps the 8-mer conserved sequence. This factor is present in murine B and T lymphocytes, macrophages, mastocytes, fibroblasts, and human B lymphocytes and macrophages. The binding site was defined by using DNase I and dimethylsulfate protection assays. The putative binding sequence is closely related to the sequence, CCAAT, which is often found associated with the promoter of a gene and is recognized by the transcriptional factors CCAAT-binding transcription factor and nuclear factor I. Oligonucleotides that contain the binding site sequences for nuclear factor I and the alpha-globin CCAAT element, however, do not compete for binding of the nuclear factor to the sequence identified here, suggesting that, in spite of the similarity of the binding sequence, the nuclear factor identified in this report may be different. This nuclear protein may be one of the trans-acting factors that mediate transcription of class II genes.

Animals↗
PubMed1988

Cytosine methylation does not affect binding of transcription factor Sp1.

DNA methylation may be a component of a multilevel control mechanism that regulates eukaryotic gene expression. We used synthetic oligonucleotides to investigate the effect of cytosine methylation on the binding of the transcription factor Sp1 to its target sequence (a G + C-rich sequence known as a "GC box"). Concatemers of double-stranded 14-mers containing a GC box successfully competed with the human metallothionein IIA promoter for binding to Sp1 in DNase I protection experiments. The presence of 5-methylcytosine in the CpG sequence of the GC box did not influence Sp1 binding. The result was confirmed using double-stranded 20-mers containing 16 base pairs of complementary sequence. Electrophoretic gel retardation analysis of annealed 28-mers containing a GC box incubated with an Sp1-containing HeLa cell nuclear extract demonstrated the formation of DNA-protein complexes; formation of these complexes was not inhibited when an oligomer without a GC box was used as a competitor. Once again, the presence of a 5-methylcytosine residue in the GC box did not influence the binding of the protein to DNA. The results therefore preclude a direct effect of cytosine methylation on Sp1-DNA interactions.

5-Methylcytosine↗
PubMed1988

Immunological detection of 22K protein in sporulating cells of Bacillus megaterium ATCC 12872.

The synthesis and deposition of 22,000-dalton (22K) spore coat protein were examined immunochemically on the sporulating cells of Bacillus megaterium ATCC 12872 using the antibody to purified 22K spore coat protein. This antibody cross-reacted with 44K and 25K proteins in immunoblot analysis of dormant spore coat proteins. Immunoblot analysis on the sporulating cells showed that 22K protein was detected from t8 in forespore coat protein fractions. Sandwich enzyme immunoassay revealed that 22K protein in the spore coat protein fraction appeared at t6 and reached a plateau at t9, and 22K protein in the mother cell cytoplasmic fraction was detected at only t7 and t8 at a very low level.

Bacillus megaterium↗
PubMed1988

Immunoelectron microscopic studies on spore coat proteins of Bacillus megaterium.

An immunochemical staining technique for the spore coat proteins of Bacillus megaterium ATCC 12872 was developed using colloidal gold as a second antibody. For reducing the non-specific immunogold binding and increasing the specific binding, the affinity-purified IgG was used as a first antibody. In sporulating cells at t10, gold particles were found not only in the spore coat but also in the mother cell cytoplasm, suggesting that some coat proteins were synthesized in the cytoplasm. Use of the specific affinity-purified antibody to 48K-protein demonstrated that this protein was one of the components of the outer coat.

Bacillus megaterium↗
PubMed1987

In vitro activation of the HIV-1 enhancer in extracts from cells treated with a phorbol ester tumor promoter.

The transition from persistent to lytic infection by the human immunodeficiency virus, HIV, is marked by a burst of viral replication and gene expression that occurs when infected cells are stimulated by physiological inducers or tumor promoters like 12-O-tetradecanoyl phorbol acetate (TPA). We report here that the HIV enhancer is activated specifically by TPA in several non-lymphoid cell types, and that this transcriptional regulation can be reproduced in a cell-free system. In vitro transcription experiments revealed a 6-fold activation of the HIV promoter in nuclear extracts prepared from TPA-induced HeLa tk- cells, whereas a control (human alpha-globin) promoter was transcribed with equal efficiency in either induced or uninduced cell extracts. A corresponding increase in the activity of a cellular DNA-binding protein that interacts with the HIV enhancer was detected in TPA-treated cells with DNase I footprint experiments. This increase occurred in the absence of de novo protein synthesis, suggesting a post-transcriptional activation mechanism. Analysis of HIV deletion mutants suggests that the enhancer is the target for the TPA effect both in vitro and in vivo. The cell-free system described here should facilitate studies on the mechanism of phorbol ester induction of gene-specific transcription factors.

Cell Line↗
PubMed1987

Transcription factor AP-2 mediates induction by two different signal-transduction pathways: protein kinase C and cAMP.

We have purified and characterized the 50 kd activator protein 2 (AP-2), another enhancer-binding protein interacting with the human metallothionein IIA (hMT-IIA) gene control region. Purified AP-2 activates transcription in vitro from a hybrid promoter containing hMT-IIA upstream sequences. AP-2 also recognizes control elements of the human growth hormone, c-myc, and H-2Kb genes, and the SV40 and bovine papilloma virus enhancers. Multiple synthetic copies of the hMT-IIA high-affinity AP-2 binding site can act as efficient, cell-type-specific enhancer elements; their activity increases after treatment of cells with phorbol ester or cAMP-elevating agents. In contrast, a synthetic enhancer recognized by factor AP-1 is activated only by phorbol ester. AP-2 appears to mediate transcriptional activation in response to two different signal-transduction pathways, one involving the phorbol-ester- and diacylglycerol-activated protein kinase C, the other involving cAMP-dependent protein kinase A.

Animals↗
PubMed1987

Phorbol ester-inducible genes contain a common cis element recognized by a TPA-modulated trans-acting factor.

The promoter regions of several phorbol diester-(TPA-) inducible genes (collagenase, stromelysin, hMT IIA, and SV40) share a conserved 9 bp motif. Synthetic copies of these closely related sequences conferred TPA inducibility upon heterologous promoters. Footprinting analysis indicated that these TPA-responsive elements (TREs) are recognized by a common cellular protein: the previously described transcription factor AP-1. A point mutation that eliminated the basal and induced activity of the TRE also interfered with its ability to bind AP-1. Treatment of cultured cells with TPA led to a rapid 3- to 4-fold increase in TRE binding activity, by a posttranslational mechanism. These results strongly suggest that AP-1 is at the receiving end of a complex pathway responsible for transmitting the effects of phorbol ester tumor promoters from the plasma membrane to the transcriptional machinery.

Animals↗