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Biomedical subjects

S Tajima

Publications and source records attributed to S Tajima.

At least 19 recordsLinked to original sources
PubMed1998

Function and Conformation of Wild-Type p53 Protein Are Influenced by Mutations in Bovine Leukemia Virus-Induced B-Cell Lymphosarcoma

The mutations of the p53 gene previously represented one of several genetic changes involved in the development of bovine leukemia virus (BLV)-induced lymphosarcoma, while the effects of these mutations on the function of p53 are unknown. We identified four mutations of p53 gene in BLV-infected cattle with lymphosarcoma and demonstrated clearly the existence of two functionally distinct groups of mutants: (i) the mutant forms with substitutions at codons 241 and 242, which were mapped within an evolutionally conserved region and corresponded to the human "hot-spot" mutations, had completely lost the capacities for transactivation and growth suppression and gained transdominant repression activity in p53-null SAOS-2 cells; and (ii) the mutations at codons 206 and 207 were located outside the evolutionally conserved regions. These mutants partially retained the capacity for transactivation and growth suppression and failed to inhibit the transactivation activity of coexpressed wild-type p53, instead showing an enhancement of this activity. In addition, protein analysis using an antibody specific for the mutant form revealed that the mutations at codons 206 and 242 induced a "mutant" conformation of the bovine p53 proteins. Collectively, these results show that mutations of p53 gene in BLV-infected cattle with lymphosarcoma can potentially alter its physiological function and may play an important role in BLV-induced leukemogenesis. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Function and conformation of wild-type p53 protein are influenced by mutations in bovine leukemia virus-induced B-cell lymphosarcoma.

The mutations of the p53 gene previously represented one of several genetic changes involved in the development of bovine leukemia virus (BLV)-induced lymphosarcoma, while the effects of these mutations on the function of p53 are unknown. We identified four mutations of p53 gene in BLV-infected cattle with lymphosarcoma and demonstrated clearly the existence of two functionally distinct groups of mutants: (i) the mutant forms with substitutions at codons 241 and 242, which were mapped within an evolutionally conserved region and corresponded to the human "hot-spot" mutations, had completely lost the capacities for transactivation and growth suppression and gained transdominant repression activity in p53-null SAOS-2 cells; and (ii) the mutations at codons 206 and 207 were located outside the evolutionally conserved regions. These mutants partially retained the capacity for transactivation and growth suppression and failed to inhibit the transactivation activity of coexpressed wild-type p53, instead showing an enhancement of this activity. In addition, protein analysis using an antibody specific for the mutant form revealed that the mutations at codons 206 and 242 induced a "mutant" conformation of the bovine p53 proteins. Collectively, these results show that mutations of p53 gene in BLV-infected cattle with lymphosarcoma can potentially alter its physiological function and may play an important role in BLV-induced leukemogenesis.

Animals↗
PubMed1998

Acquisition of secretion of transforming growth factor-beta 1 leads to autonomous suppression of scavenger receptor activity in a monocyte-macrophage cell line, THP-1.

Macrophage cells derived from the human monocytic leukemia cell line, THP-1, accumulate esterified cholesterol when cultivated in the presence of acetylated low density lipoprotein (Ac-LDL) through scavenger receptors (ScR). In the present study, we isolated a subtype of THP-1 cells that failed to accumulate esterified cholesterol when cultivated in the presence of Ac-LDL. The cells had negligible amounts of cell association and degradation of Ac-LDL compared with the parent THP-1 cells. The subtype THP-1 cells did not express ScR mRNA as well as that of lipoprotein lipase. In contrast, the expression of apolipoprotein E mRNA was greater than that found in parent THP-1 cells. The culture medium of subtype THP-1 cells treated with 12-O-tetradecanoylphorbol-13-acetate inhibited the uptake of Ac-LDL and the expression of ScR in parent THP-1 cells. After a 48-h incubation in the culture medium containing 12-O-tetradecanoylphorbol-13-acetate, the culture medium of differentiated subtype THP-1 cells contained 6.9 ng/ml transforming growth factor (TGF)-beta 1, while that of parent THP-1 cells secreted below detection level, which was less than 3 ng/ml. This inhibitory effect of the conditioned medium on the expression of ScR in parent THP-1 cells was abolished by pretreatment of the culture medium with anti-TGF-beta 1 antibodies. Parent THP-1 cells expressed as much TGF-beta 1 mRNA as sTHP-1 cells after stimulation of differentiation. Although the precursor forms of TGF-beta 1 that were synthesized in both parent and subtype THP-1 cells were of similar size and were expressed at similar levels, latent TGF-beta 1-binding protein, which is necessary for the secretion of TGF-beta 1, could only be co-immunoprecipitated with anti-TGF-beta 1 antibody from subtype THP-1 cells. This suggests that subtype THP-1 cells secrete TGF-beta 1 into the medium by forming a functional complex with the latent TGF-beta 1-binding protein. We conclude that subtype THP-1 cells could not take up Ac-LDL because ScR was inhibited (leading to a loss of function) caused by the secreted TGF-beta 1.

Carrier Proteins↗
PubMed1997

Stimulation of human keratinocyte growth by alginate oligosaccharides, a possible co-factor for epidermal growth factor in cell culture.

Oligosaccharides, involved in regulation of plant developmental and defensive processes, were tested to determine their ability to enhance proliferation of human keratinocytes. A mixture of alginate oligosaccharides remarkably stimulated keratinocyte growth and [3H]thymidine uptake in the presence of epidermal growth factor (EGF). The activity was comparable to bovine pituitary extract, a common complement in keratinocyte culture, and additive on BPE-induced stimulation. The most effective oligosaccharide in the mixture was identified and its chemical structure was determined. These findings demonstrate a novel activity of alginate oligosaccharide(s) in keratinocyte growth and suggest a possible co-factor for EGF-dependent stimulation in medium for keratinocytes.

Alginates↗
PubMed1997

Quantification of 1,5-anhydro-D-glucitol in urine by automated borate complex anion-exchange chromatography with an immobilized enzyme reactor.

HPLC using a borate form of a strongly anion-exchange resin column and an immobilized enzyme reactor for colorimetric detection was used to quantify urinary 1,5-anhydro-D-glucitol. Urine samples were introduced into the system every 7 min without any pretreatment, and after separation of interfering substances in the column, 1,5-anhydro-D-glucitol was successively detected. Quantitative determination of urinary 1,5-anhydro-D-glucitol was possible within the 1.2-300 micromol/l range. The coefficient of variance was less than 3% and the correlation between results obtained with our system (y) and those obtained by gas chromatography-mass spectrometry (x) was y=0.983x-1.287 micromol/l (n=42, r=0.998).

Borates↗
PubMed1997

Genomic organization of the mouse AZ1 gene that encodes the protein localized to preacrosomes of spermatids.

The AZ1 protein is localized to the preacrosome region of spermatids. Previous developmental studies suggested that AZ1 gene transcription begins in pachytene spermatocytes and that expression of the gene is induced in cultivated fibroblasts on treatment with 5-azacytidine, which is known to lead to the demethylation of genomic DNA. In the present study, we cloned the gene coding AZ1 cDNA and elucidated its genomic organization. AZ1 cDNA was encoded by 25 exons distributed within 25 kb of genomic DNA. The transcription started at nucleotide positions -312 and -311 of the cDNA, with the A of the ATG codon specifying the initiator methionine assigned as nucleotide position +1. Exon 1 and a part of intron 1 of the AZ1 gene constituted a typical CpG island, and an about 0.2-kb sequence of the 5'-proximal region exhibited a G + C content and CpG ratio higher than the averages for the mammalian genomic sequence.

Acrosome↗
PubMed1997

Decrease in elastin gene expression and protein synthesis in fibroblasts derived from cardinal ligaments of patients with prolapsus uteri.

Abnormal connective tissues may be a key factor in the development of pelvic supportive disorders. Elastin gene transcripts and elastin synthesis in cultured fibroblasts derived from cardinal ligaments of patients with prolapsus uteri and compared them with those in fibroblasts from age-matched control patients were examined. Elastin mRNA steady-state levels and elastin synthesis were significantly down-regulated in quiescent fibroblasts from prolapsus uteri patients compared with quiescent control fibroblasts. Although transforming growth factor beta 1 (TGF-beta 1) promoted elastin mRNA and protein levels in fibroblasts from both prolapsus uteri and control patients, the maximum levels of elastin gene transcripts and elastin synthesis in response to exogenous TGF-beta 1 were significantly lower in prolapsus uteri fibroblasts than control fibroblasts. These results suggest that the marked reduction in elastin gene transcripts and elastin production in fibroblasts cultured from elderly women with prolapsus uteri could lead to a paucity of ligament elastic fibres and thus may contribute to the loss of supportive function in uterine connective tissues.

Cells, Cultured↗
PubMed1997

Stimulation of collagen expression and glycosaminoglycan synthesis by midkine in human skin fibroblasts.

Midkine is a retinoid-inducible regulator of cell differentiation and cell growth in developing embryonic tissues. The effects of midkine on the expression of the extracellular matrix components, collagens and glycosaminoglycans, in dermal fibroblasts were studied. Midkine did not alter fibroblast proliferation. Collagen synthesis was stimulated in a dose- and exposure time-dependent manner and the maximum two-fold stimulation was achieved at a concentration of 100 ng/ml for 72 h treatment. Midkine increased the synthesis of type I and III collagens to the same extent. Glycosaminoglycan synthesis was also stimulated two-fold, mainly accounted for by an increase in hyaluronan synthesis. Midkine enhanced mRNA levels of alpha 1 (I), alpha 1 (III), alpha 1 (VI) collagens, transforming growth factor beta 1 and matrix metalloprotease-2 but did not alter the mRNA levels of elastin, MMP-1 and tissue inhibitor of metalloproteases-1. These results suggest that midkine is a potent stimulator of collagen and glycosaminoglycan synthesis and may prove useful in the therapy of delayed wound healing.

Carrier Proteins↗
PubMed1997

Expression of the retinoid-inducible polypeptide, midkine, in human epidermal keratinocytes.

Midkine (MK) is a retinoid-inducible and potent cell growth/differentiation factor active during mouse embryogenesis. We studied MK expression in various cell strains established from the skin. MK and its mRNA were detected in cultured keratinocytes but not in melanoma cell lines or dermal fibroblasts by both Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). Treatment of cultured keratinocytes with retinoic acid (10(-5) M, 24 h) resulted in an increase in the level of MK mRNA. When added to cultured keratinocytes, MK stimulated cell proliferation fourfold. Immunohistochemistry revealed MK to be present at the epidermal-dermal junction in embryonic mouse skin and in normal human skin. The limited expression of MK in epidermal keratinocytes indicates that this polypeptide may be involved in the differentiation/proliferation of keratinocytes.

Animals↗
PubMed1997

Smooth muscle cell proliferation, elastin formation, and tropoelastin transcripts during the development of intimal thickening in rabbit carotid arteries after endothelial denudation.

Extracellular matrix formation and smooth muscle cell proliferation are two major factors contributing to the development of intimal thickening after arterial injury. We investigated the elastin formation, tropoelastin transcripts, and proliferation of smooth muscle cells during the development of intimal thickening in rabbit carotid arteries after balloon endothelial denudation. Tropoelastin transcripts, identified by in situ hybridization using a digoxigenin-labeled probe, and elastin staining in the thickened intima were minimal 1 week after endothelial denudation when smooth muscle cell proliferation appeared throughout the thickened intima. A strong signal for tropoelastin transcripts was seen in the basal layer of the thickened intima 2 weeks after endothelial denudation, and then in the surface layer of the thickened intima 4 weeks after endothelial denudation. Immunohistochemistry for proliferating cell nuclear antigen and Ki-67, both markers for proliferating cell nuclei, showed that tropoelastin transcripts and elastin formation increased when smooth muscle cells enter quiescence after the end of the proliferative phase in the intima. Our findings strongly suggest that elastin synthesis and smooth muscle cell proliferation are tightly regulated during the repair of arterial wall injury.

Animals↗
PubMed1997

Elastin expression is up-regulated by retinoic acid but not by retinol in chick embryonic skin fibroblasts.

Effects of retinoid derivatives (retinol and retinoic acid) on elastin expression and cell proliferation in chick embryonic skin fibroblasts were studied. Retinoic acid inhibited cell proliferation one half of control at the concentration 10(-5) M. Retinoic acid exhibited stimulatory effect on elastin synthesis with a maximum stimulation of 2.0-fold at the concentration of 10(-6) M for 24 h treatment. Elastin level detected by Western blot analysis in the pooled conditioned medium was compatible with the increase of elastin synthesis by retinoic acid treatment. Comparable increase in elastin mRNA level was observed by retinoic acid treatment. Retinol showed no significant effects on either cell proliferation or elastin expression. The results indicate that retinoic acid was potentially active and retinol was inactive for modulation of cell proliferation and elastin expression.

Animals↗
PubMed1997

Effects of monensin on tropoelastin metabolism in vascular smooth muscle cells: monensin causes intracellular degradation of accumulated tropoelastin.

Treatment with 80 nM monensin for 48 h resulted in impairment of tropoelastin secretion during the initial 6 h and subsequent reduction of tropoelastin synthesis from 18 to 48 h to one-tenth. The steady state level of tropoelastin mRNA started to decrease at 6 h and reached one-fifth of the control level by 48 h. A pulse-chase experiment after 24 h monensin treatment demonstrated that half of the accumulated tropoelastin in the cells was rapidly degraded within 120 min. These results indicate that the marked reduction in tropoelastin synthesis from 6 to 48 h treatment may be caused by both a reduction in the tropoelastin mRNA level and accelerated intracellular degradation of tropoelastin. Thus, monensin modulates tropoelastin expression through pretranslational and posttranslational mechanisms.

Animals↗
PubMed1997

Expression of a gene for uricase II (nodulin-35) in cotyledons of soybean plants.

A cDNA clone (URcot-35) was isolated from a soybean cotyledonary cDNA library using a cDNA clone (URnod-35) for nodule uricase II as a probe. URcot-35 was a 1,170-bp cDNA with an open reading frame that encoded a protein of putative 309 amino acids with a molecular mass of 35,137 Da. The nucleotide sequence of URcot-35 was identical to that of URnod-35. Expression of the URcot-35 gene in cotyledons was investigated by Northern dot-blot hybridization, by the reverse transcription-polymerase chain reaction with subsequent hybridization assays with the cDNA for nodule uricase II as a probe, and by immunoblotting analysis with a monoclonal antibody that was specific to nodule uricase II. The results suggested that the transcript of URcot-35 was present in developing cotyledons and that uricase II accumulated during the pod-filling stage. This is the first report of the isolation of cDNA for uricase II from non-symbiotic tissue and the results demonstrate that uricase II in soybean cotyledons is identical to that in soybean nodules.

Amino Acid Sequence↗
PubMed1997

Two distinct uricase II (nodulin 35) genes are differentially expressed in soybean plants.

Nodule-specific uricase (uricase II) is a homotetramer of a 33-kDa polypeptide, nodulin 35, and plays a key role in the assimilation of nitrogen fixed by microsymbionts in most legumes that have determinate nodules. We have isolated two distinct genes, UR2 and UR9, that encode for nodulin 35 from a soybean genomic library. Their corresponding cDNAs were also isolated from a nodule cDNA library. UR2 and UR9 both encode for 309 amino acid proteins with 12 amino acid differences. The expression of these two genes in various organs of soybean was examined by reverse transcription-polymerase chain reaction with primers specific to each cDNA sequences. Expression of UR9 was almost specific in root nodules, although it was expressed in roots, primary leaves, and developing seed at very low levels. In contrast, the UR2 transcripts were present in almost all plant organs at low levels, but no enhancement of the expression was observed in nodules. Thus, UR9 behaves as a nodulin gene, whereas UR2 is a nonsymbiotic uricase II gene. The sequences of their potential promoter regions share high homology within regions up to about 400 bp upstream from the translation initiation sites. These results suggest that symbiotic and nonsymbiotic uricase II genes diverged by gene duplication and that relatively small alterations in the promoter sequence enable the nodule-specific expression.

Amino Acid Sequence↗
PubMed1997

Exposure of fibroblasts derived from keloid patients to low-energy electromagnetic fields: preferential inhibition of cell proliferation, collagen synthesis, and transforming growth factor beta expression in keloid fibroblasts in vitro.

We studied the effects of electromagnetic fields (EMFs) on cell proliferation and collagen synthesis in both normal and keloid fibroblasts in vitro. Treatment of keloid fibroblasts with 60-Hz EMFs for 10 days resulted in the inhibition of cell proliferation, whereas no significant change in cell proliferation of normal fibroblasts was observed. EMFs inhibited collagen synthesis in keloid fibroblasts but not in normal fibroblasts without altering the ratio of type III to type I collagen, indicating that EMFs inhibit type I and type III collagen synthesis to the same extent. EMFs also decreased the expression of transforming growth factor beta (TGF-beta) in keloid fibroblasts. These results suggest that EMFs may have a useful therapeutic potential for the treatment of keloid.

Adolescent↗
PubMed1997

The influence of arterial inflow and venous outflow on the survival of reversed-flow island flaps: an experimental study.

Reversed-flow flaps are currently used for reconstruction of the distal portion of the upper and lower extremities. However, detailed experimental studies on the reversed-flow flap are lacking, and there have been many clinical reports concerning its postoperative complications. In the present study, the effects of blood inflow and outflow on flap viability were investigated. Six groups of island flaps, which differed in whether arterial inflow and venous outflow were retrograde or antegrade, were prepared on the rat's abdomen. The venous pressure of the vascular pedicle (n = 5), the blood flow (n = 10), and the survival rates of flaps (n = 10) were measured in each group. When arterial inflow was retrograde, the viable flap area diminished in proportion to the decrease in blood flow. The correlation coefficient between blood flow and survival rates of the flaps was 0.885, which indicates that blood inflow to the flap is closely related to the area of flap viability. The relationship between the venous outflow and the viable flap area was "all or nothing". When venous outflow was retrograde, there was either no effect on flap area at all or complete congestive necrosis.

Abdomen↗