Search PubMed⌕ Search

Biomedical subjects

S Oikawa

Publications and source records attributed to S Oikawa.

At least 37 records · Page 2Linked to original sources
PubMed2001

Discovery of a non-peptide small molecule that selectively mimics the biological actions of calcitonin.

Calcitonin (CT), a 32-amino acid peptide hormone secreted mainly from the thyroid gland, plays an important role in maintaining bone homeostasis. To discover non-peptide small molecules with biological actions similar to those of CT, a cell-based screening of an in-house chemical library was performed and a pyridone derivative (SUN B8155) was identified. Like CT, it elevated cyclic AMP (cAMP) levels in T47D and UMR106-06 cells which endogenously express human and rat CT receptor, respectively. SUN B8155 also stimulated cAMP formation in cells expressing recombinant human CT receptor, but not in those expressing human parathyroid hormone/parathyroid hormone-related peptide receptor. Accumulation of cAMP in T47D cells was blocked by a selective antagonist of CT receptor, salmon CT(8-32), whereas SUN B8155 did not displace the specific binding of [(125)I]CT to the receptor. Our results suggested that the compound selectively interacts with the CT receptor by a mechanism similar to but probably different from that of CT itself. In rats, intraperitoneal administration of SUN B8155 significantly lowered serum calcium levels, like CT. Our results demonstrate, for the first time, that the biological activities of the newly identified small molecule can mimic that of CT, acting via the CT receptor.

Animals↗
PubMed2001

Site-specific DNA damage at the GGG sequence by UVA involves acceleration of telomere shortening.

Telomere shortening is associated with cellular senescence. We investigated whether UVA, which contributes to photoaging, accelerates telomere shortening in human cultured cells. The terminal restriction fragment (TRF) from WI-38 fibroblasts irradiated with UVA (365-nm light) decreased with increasing irradiation dose. Furthermore, UVA irradiation dose-dependently increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in both WI-38 fibroblasts and HL-60 cells. To clarify the mechanism of the acceleration of telomere shortening, we investigated site-specific DNA damage induced by UVA irradiation in the presence of endogenous photosensitizers using (32)P 5'-end-labeled DNA fragments containing the telomeric oligonucleotide (TTAGGG)(4). UVA irradiation with riboflavin induced 8-oxodG formation in the DNA fragments containing telomeric sequence, and Fpg protein treatment led to chain cleavages at the central guanine of 5'-GGG-3' in telomere sequence. The amount of 8-oxodG formation in DNA fragment containing telomere sequence [5'-CGC(TTAGGG)(7)CGC-3'] was approximately 5 times more than that in DNA fragment containing nontelomere sequence [5'-CGC(TGTGAG)(7)CGC-3']. Catalase did not inhibit this oxidative DNA damage, indicating no or little participation of H(2)O(2) in DNA damage. These results indicate that the photoexcited endogenous photosensitizer specifically oxidizes the central guanine of 5'-GGG-3' in telomere sequence to produce 8-oxodG probably through an electron-transfer reaction. It is concluded that the site-specific damage in telomere sequence induced by UVA irradiation may participate in the increase of telomere shortening rate.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Identification of a novel inhibitor of LPS-induced TNF-alpha production with antiproliferative activity in monocyte/macrophages.

An isoquinoline derivative, 5-methyl-7,8-dimethoxy-1-phenylpyrazolo[5,4-c]isoquinoline (compound 1), was identified as a novel inhibitor of LPS-induced TNF-alpha production by cell-based screening. Compound 1 suppressed LPS-induced TNF-alpha production in RAW264.7 cells and murine peritoneal macrophages in a dose-dependent manner similar to SB203580, known as a specific inhibitor of p38 MAPK. It also inhibited an LPS-induced increase in serum TNF-alpha in a mouse endotoxic shock model with an ED(50) of approximately 10 mg/kg. Compound 1 had little effect on the incorporation of [3H]-leucine into the cells, while it suppressed LPS-induced TNF-alpha mRNA levels in RAW264.7 cells. The results indicate that suppression of TNF-alpha production was not a result of nonspecific inhibition of de novo translation but was based on the decreased TNF-alpha mRNA levels. The in vitro kinase assay revealed that compound 1 did not strongly inhibit p38 MAPK activity, its potency being much lower than that of SB203580, suggesting that the TNF-alpha-suppressive action of compound 1 cannot be attributed to the inhibition of p38 MAPK. Furthermore, in contrast to SB203580, it significantly inhibited the growth of RAW264.7 and THP-1 cells in a cytostatic manner. Compound 1 is likely to have antiinflammatory and antiproliferative effects by acting on some molecule other than p38 MAPK that contributes to both LPS-induced TNF-alpha production and the cell growth of monocyte/macrophages.

Activating Transcription Factor 2↗
PubMed2001

Amplification of bleomycin-induced DNA cleavage at cytosine residues 3' to GGG sequences by pyrrole triamide.

We investigated the amplification of bleomycin-induced DNA cleavage by synthetic triamides containing N-methylpyrrole (Py) and/or N-methylimidazole (Im), PyPyPy, PyPyIm, PyImPy, and PyImIm, using 32P-labeled DNA fragments obtained from the human c-Ha-ras-1 and p53 genes. Peplomycin, a bleomycin analog, plus Fe(II) caused DNA cleavage at the 5'-GC-3' and 5'-GT-3' sequences (damaged bases are underlined). The addition of PyPyPy dramatically enhanced the cleavage, particularly at cytosine residues 3' to consecutive guanines. Alteration in the site specificity was not observed with other triamides (PyPyIm, PyImPy, and PyImIm). DNase I footprinting revealed that PyPyPy bound to the sites adjacent to the sites where DNA cleavage was enhanced by PyPyPy, and that PyPyPy enhanced DNase I-induced cleavage in GC-rich regions. These findings suggest that binding of PyPyPy to the DNA minor groove changes the DNA conformation to allow peplomycin to cleave DNA more efficiently at GC-rich sequences, resulting in intensive site-specific DNA cleavage particularly at cytosines at the 3'-side of polyguanines. The present study on amplifiers of antitumor drugs would appear to offer a novel approach to the establishment of more effective chemotherapy.

Antimetabolites, Antineoplastic↗
PubMed2001

Generation of polyclonal antiserum against the growth hormone secretagogue receptor (GHS-R): evidence that the GHS-R exists in the hypothalamus, pituitary and stomach of rats.

Growth hormone (GH) secretagogues (GHSs), which stimulate GH secretion, are synthetic compounds that act through the GHS receptor (GHS-R) which has been recently cloned. We raised an antiserum in a rabbit against a synthetic peptide corresponding to amino acid residues 248-260 of the third intracellular loop of the rat GHS-R. A competitive immunoassay showed that the antiserum had a specific affinity for the target peptide. To confirm the specificity of the antiserum, the GHS-R cDNA was stably expressed in COS-7 cells. In Western blot analysis, the band was detected at 44 kDa in the extracts from COS-7 cells expressing GHS-R (COS-7/tf3-2) but not in those from wild-type COS-7 cells. Furthermore, while COS-7/tf3-2 cells were strongly immunostained for GHS-R, no GHS-R-like immunoreactivity was observed in wild-type COS-7 cells. Immunoreactive bands were also observed at approximately 46 kDa in the extracts from rat hypothalamus, pituitary and stomach by Western blot analysis. These studies are the first to show the existence of GHS-R protein in the stomach. The antiserum for the GHS-R is sensitive and specific, and it would be useful for clarifying the roles of GHS/ghrelin.

Animals↗
PubMed2001

Histological study on local invasiveness of clival chordoma. Case report of autopsy.

BACKGROUND: It is well known that clival chordomas invade bony structures; however, their invasiveness of other structures has rarely been reported. We report an autopsy case of clival chordoma in a 61-year-old woman, who underwent surgery 6 times for a period of 8 years, with special reference to its local invasiveness. METHOD AND FINDINGS: The histological studies showed that the tumour grew in the loose connective tissue in multilayers or multilobular fashion, invading the submucous layer in addition to the bone; however, it did not invade other soft tissue, particularly vital neurovascular structures or the dura itself, even in the advanced stage. INTERPRETATION: The dura may serve as a strong barrier against tumour invasion into the intradural space, which emphasises the importance of not injuring the dura, when the tumour is removed extradurally. For radical removal of clival chordoma, it will be necessary to remove the tumour extensively including normal bone and soft tissues surrounding the tumour, especially the mucous membrane, because the normal mucous membrane is surgically difficult to preserve by dissecting it from the invaded submucous layer.

Autopsy↗
PubMed2001

Molecular cloning of bovine (Bos taurus) cDNA encoding a 94-kDa glucose-regulated protein and developmental changes in its mRNA and protein content in the mammary gland.

We isolated and sequenced cDNA clones encoding a 94-kDa glucose-regulated protein (GRP94) from a cDNA library constructed using bovine (Bos taurus) mammary gland poly(A)(+) RNA. The coding nucleotide sequence and the deduced amino acid sequence of bovine GRP94 shared 94.2-88.4% and 98.1-96.5% identity with those of other mammalian species, respectively. The primary structure contained a carboxyl-terminal signal sequence for retention in the endoplasmic reticulum, six potential sites for N-linked glycosylation and two potential adenosine 5'-triphosphate binding sites, similar to other mammalian and avian GRP94 homologues. In Northern blot hybridization using a cDNA probe from the bovine GRP94 cDNA sequence, a transcript 3.0 kb in size was detected. We measured the amounts of GRP94 and its mRNA in mammary glands from cows at various developmental stages of hormonally induced lactation. The highest level of GRP94 mRNA, determined by dot blot analysis, was detected in the developing stage. In contrast to the mRNA level, the amount of protein, determined by immunoblot analysis using rabbit antiserum raised against GRP94 purified from bovine brain, was higher in lactating stages than in others. The increased level of GRP94 mRNA during the developing stage and the maintenance of GRP94 protein during lactation suggest that the synthesis of GRP94 is regulated during mammary development and differentiation, and also that the protein is involved in a function related to lactation.

Amino Acid Sequence↗
PubMed2001

Mechanism of guanine-specific DNA damage by oxidative stress and its role in carcinogenesis and aging.

Reactive species generated by chemicals and UV radiation can cause sequence-specific DNA damage and play important roles in mutagenesis, carcinogenesis and aging. We have investigated sequence specificity of oxidative stress-mediated DNA damage by using 32P-labeled DNA fragments obtained from the human c-Ha-ras-1 and p53 genes. Free hydroxyl radical causes DNA damage with no marked site specificity. Reactive nitrogen species, sulfate radicals, nitrogen-centered radicals, benzoyloxyl radical and alkoxyl radical show different sequence specificity. Benzoyloxyl radical specifically causes damage to the 5'-G in GG sequence. UVA radiation also causes DNA damage at this site through electron transfer in the presence of certain photosensitizers. The 5'-G in GG sequence is easily oxidized because a large part of the highest occupied molecular orbital is distributed on this site. On the basis of these findings, the sequence specificity of DNA damage is presumably determined by (a) redox potential of reactive species; (b) ionization potential of DNA bases; and (c) site-specific binding of metal ion to DNA. Here we discuss the mechanisms of sequence-specific DNA damage in relation to carcinogenesis and aging.

Aging↗
PubMed2001

HHV8-negative primary effusion lymphoma of the peritoneal cavity presenting with a distinct immunohistochemical phenotype.

Primary effusion lymphoma (PEL) has been recognized as a body-cavity-based lymphoma that was originally reported to be associated with human herpes virus 8 (HHV8) infection, and was frequently found in human immunodeficiency virus-positive (HIV) patients. Here we describe an autopsy case of PEL of the peritoneal cavity in an immunocompetent patient. Cytological analysis of tumor cells within ascites revealed immunocytochemical features of keratin positivity and CD45 negativity. At autopsy, the presence of a massive volume of ascites as well as diffuse tumor cell infiltrates within the serosa of the intestine and mesenterium were observed. Tumor cells were morphologically similar to anaplastic large-cell lymphoma, but were immunohistochemically positive for keratin and epithelial membrane antigen (EMA). They also showed no reactivity to representative lymphocyte surface markers including CD45, in addition to being negative for CD30 and p80NPM/ALK. Molecular analysis of the tumor cells revealed monoclonality of the immunoglobulin heavy-chain gene rearrangement which demonstrated a lymphoma of the B-cell lineage. Furthermore, HHV8 was not detected by immunohistochemical analysis, PCR or nested PCR technique. Based on these results, we consider the present case to be an HHV8-negative PEL with keratin and EMA positivity.

Adult↗
PubMed2001

Skull base techniques for multiple aneurysms in the internal carotid juxta-dural ring region.

The aneurysm located in the internal carotid juxta-dural ring region is difficult to surgically obliterate. At surgery, careful drilling of the anterior clinoid process is mandatory, especially when a laterally projecting aneurysm protrudes to or inside the anterior clinoid process.In this paper, treatment procedures using the skull base techniques with intravascular coil embolisation are described by showing a case.

Carotid Artery, Internal↗
PubMed2001

Site specificity and mechanism of oxidative DNA damage induced by carcinogenic catechol.

Catechol, a naturally occurring and an important industrial chemical, has been shown to have strong promotion activity and induce glandular stomach tumors in rodents. In addition, catechol is a major metabolite of carcinogenic benzene. To clarify the carcinogenic mechanism of catechol, we investigated DNA damage using human cultured cell lines and 32P-labeled DNA fragments obtained from the human p53 and p16 tumor suppressor genes and the c-Ha-ras-1 proto-oncogene. Catechol increased the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), which is known to be correlated with the incidence of cancer, in a human leukemia cell line HL-60, whereas the amount of 8-oxodG in its hydrogen peroxide (H2O2)-resistant clone HP100 was not increased. The formation of 8-oxodG in calf thymus DNA was increased by catechol in the presence of Cu(2+). Catechol caused damage to 32P-labeled DNA fragments in the presence of Cu(2+). When NADH was added, DNA damage was markedly enhanced and clearly observed at relatively low concentrations of catechol (<1 microM). DNA cleavage was enhanced by piperidine treatment, suggesting that catechol plus NADH caused not only deoxyribose phosphate backbone breakage but also base modification. Catechol plus NADH frequently modified thymine residues. Bathocuproine, a specific Cu(+) chelator and catalase inhibited the DNA damage, indicating the participation of Cu(+) and H2O2 in DNA damage. Typical hydroxyl radical scavengers did not inhibit catechol plus Cu(2+)-induced DNA damage, whereas methional completely inhibited it. These results suggest that reactive species derived from the reaction of H2O2 with Cu(+) participates in catechol-induced DNA damage. Therefore, we conclude that oxidative DNA damage by catechol through the generation of H2O2 plays an important role in the carcinogenic process of catechol and benzene.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Preservation of large bridging veins of the cranial base: technical note.

OBJECTIVE: Sacrifice of a bridging vein in the cranial base occasionally may cause significant postoperative morbidity. We report a simple method for preserving large bridging veins of the cranial base by reflecting the dura when a subtemporal or transsylvian approach is used. METHODS: In the subtemporal approach, when a larger bridging vein enters the dura attached to the bone of the temporal base before it empties into the dural sinus, the dura is dissected widely from the bone and is cut vertically toward the medial side of the temporal base in front of the entrance of the vein into the dura. The dura, which includes part of the entrance and interdural course of the vein, is reflected and retracted over the brain. In the transsylvian approach, when the bridging segment of the superficial sylvian vein becomes taut because of retraction of the temporal lobe, the dura is incised along the sphenoid ridge and is dissected and freed from the sphenoid bone. RESULTS AND CONCLUSION: This dura-reflecting technique facilitates brain retraction without exerting tension on the bridging vein of the cranial base and is expected to help avoid injury to bridging veins during neurosurgical procedures.

Humans↗
PubMed2001

Hydroxyurea induces site-specific DNA damage via formation of hydrogen peroxide and nitric oxide.

Hydroxyurea is a chemotherapeutic agent used for the treatment of myeloproliferative disorders (MPD) and solid tumors. The mutagenic and carcinogenic potential of hydroxyurea has not been established, although hydroxyurea has been associated with an increased risk of leukemia in MPD patients. To clarify whether hydroxyurea has potential carcinogenicity, we examined site-specific DNA damage induced by hydroxyurea using (32)P-5'-end-labeled DNA fragments obtained from the human p53 and p16 tumor suppressor genes and the c-Ha-ras-1 protooncogene. Hydroxyurea caused Cu(II)-mediated DNA damage especially at thymine and cytosine residues. NADH efficiently enhanced hydroxyurea-induced DNA damage. The DNA damage was almost entirely inhibited by catalase and bathocuproine, a Cu(I)-specific chelator, suggesting the involvement of hydrogen peroxide (H(2)O(2)) and Cu(I). Typical free hydroxyl radical scavengers did not inhibit DNA damage by hydroxyurea, but methional did. These results suggest that crypto-hydroxyl radicals such as Cu(I)-hydroperoxo complex (Cu(I)-OOH) cause DNA damage. Formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was induced by hydroxyurea in the presence of Cu(II). An electron spin resonance spectroscopic study using N-(dithiocarboxy)sarcosine as a nitric oxide (NO)-trapping reagent demonstrated that NO was generated from hydroxyurea in the presence and absence of catalase. In addition, the generation of formamide was detected by both gas chromatography-mass spectrometry (GC-MS) and time-of-flight-mass spectrometry (TOF-MS). A high concentration of hydroxyurea induced depurination at DNA bases in an H(2)O(2)-independent manner, and endonuclease IV treatment led to chain cleavages. These results suggest that hydroxyurea could induce base oxidation as the major pathway of DNA modification and depurination as a minor pathway. Therefore, it is considered that DNA damage by hydroxyurea participates in not only anti-cancer activity, but also carcinogenesis.

Animals↗
PubMed2001

Regulation of the ghrelin gene: growth hormone-releasing hormone upregulates ghrelin mRNA in the pituitary.

Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor (GHS-R), was originally purified from the rat stomach. Ghrelin specifically releases GH following intravenous administration, and its GH-releasing activity in vivo is dependent on growth hormone-releasing hormone (GHRH). We previously reported that the expression of the GHS-R gene in the pituitary is developmentally regulated and GHRH infusion increases pituitary levels of GHS-R mRNA. Ghrelin mRNA and peptide have recently been detected in rat and human pituitaries. However, the regulation of the ghrelin gene in the pituitary is unknown. In this study, pituitary levels of ghrelin mRNA were measured with the reverse transcriptase-polymerase chain reaction in male rats at embryonic day (e)18 and postnatal days 1, 10, 30, and 75. The highest concentrations of ghrelin mRNA in the pituitary were observed at e18 and then they declined with age. The infusion of GHRH (10 microg/h, 4h) in freely-moving adult male rats resulted in a 1.9-fold increase in ghrelin mRNA levels relative to control rats (P < 0.05). These data indicated that the expression of the ghrelin gene in the pituitary is developmentally regulated and the pituitary ghrelin/GHS-R signaling system could modulate the regulation of GH secretion by GHRH.

Aging↗
PubMed2001

Trichorzin HA V, a member of the peptaibol family, stimulates intracellular cAMP formation in cells expressing the calcitonin receptor.

By a cell-based screening of an in-house natural product library, trichorzin HA V, belonging to a peptaibol family, was isolated from a strain of fungus Trichoderma as a calcitonin (CT) agonist. Like CT, trichorzin HA V elevated cAMP levels in T47D cells which endogenously express the human CT receptor. It also stimulated cAMP formation in cells expressing recombinant human CT receptor, but not in those that do not express the receptor, suggesting that it selectively interacts with the CT receptor. In contrast to trichorzin HA V, alamethicin, another well-characterized peptaibol, showed no cAMP-elevating activity at all. These results suggest that, although there was little amino acid sequence similarity between trichorzin HA V and CT, the biological activity of trichorzin HA V can mimic that of CT, acting via the CT receptor.

Animals↗
PubMed2001

Decreased concentration of serum apolipoprotein C-III in cows with fatty liver, ketosis, left displacement of the abomasum, milk fever and retained placenta.

Apolipoprotein (apo) C-III is a low molecular mass protein mainly distributed in the high-density lipoprotein (HDL) fraction. In cows with postparturient diseases such as ketosis, concentrations of cholesterol, phospholipids and apoA-I and the activity of lecithin:cholesterol acyltransferase, which are mainly distributed in or functionally associated with HDL, are reduced. The purpose of the present study was to examine whether the serum concentration of apoC-III was similarly decreased in the postparturient diseases. Compared with healthy controls, the apoC-III concentration was significantly (P<0.01) decreased in cows with fatty liver, ketosis, left displacement of the abomasum, milk fever and retained placenta. Concentrations of apoC-III in the HDL fractions from diseased cows were also lower than in controls. Of the diseased cows, the decreased apoC-III concentration was particularly distinct in cows with milk fever. Increased nonesterified fatty acid and reduced free cholesterol, cholesteryl ester and phospholipid concentrations were observed in cows with milk fever, as in the other diseased cows. The decrease in the apoC-III concentration is suggested to be closely associated with the postparturient disorders, in particular with milk fever.

Abomasum↗
PubMed2001

Effect of glucose concentration on foam cell formation in THP-1 cells.

We investigated whether a high glucose condition could affect cholesterol ester (CE) synthesis and accumulation of cholesterol in arterial wall cells by using the human monocytic cell line THP-1. After 24-hour PMA treatment, cells were grown in control (200 mg/dl of glucose) or high glucose concentration (400, 600, 800, or 1,600 mg/dl) medium for 6 days. CE synthesis was then investigated in cells incubated with 50 microg/ml of native, glycated, acetylated, or oxidized LDL. Cells grown in 400 mg/dl of glucose showed a significant increase of CE synthesis regardless of whether they were incubated with native, glycated or oxidized LDL, compared with cells grown in 200 mg/dl of glucose. In parallel with the studies of CE synthesis, the intracellular accumulation of CE also increased in cells grown in 400 mg/dl of glucose when incubated with oxidized LDL (50 microg/ml), compared with that in cells grown in 200 mg/dl of glucose. The amount of oxidized LDL associated with cells grown in 400 mg/dl of glucose was markedly higher than that in cells grown in 200 mg/dl of glucose. This suggests that there is an optimal glucose concentration (400 mg/dl) which increases the number of some scavenger receptors (receptors for oxidized LDL) expressed on cells, and might increase and stimulate CE synthesis, resulting in intracellular accumulation of CE in macrophage. A high blood glucose concentration could change the metabolism of arterial wall cells and play an important role in the pathogenesis of vascular complications of diabetes mellitus.

Cell Line↗