Search PubMed⌕ Search

Biomedical subjects

K Umezawa

Publications and source records attributed to K Umezawa.

At least 37 records · Page 2Linked to original sources
PubMed2000

Synthesis and biological activities of hapalosin derivatives with modification at the C12 position.

Among the hapalosin derivatives synthesized, the compounds carrying methyl (5a), methylthioethyl (5d) and phenylmethyl (5e) groups at the C12 position possess only the cis-peptide structure, in contrast to the cases of 5b and 5c. In addition to their conformational stability, the biological activities of the compounds were determined in relation of the P-glycoprotein-mediated MDR-reversing activity and induction of apoptosis.

Antineoplastic Agents↗
PubMed2000

A new bioactive steroidal saponin, furcreastatin, from the plant Furcraea foetida.

Microbial and plant secondary metabolites were screened for compounds that are selectively cytotoxic to mutant p53-expressing mouse fibroblasts. As a result, furcreastatin, a novel steroidal saponin, was isolated from an EtOH extract of the leaves of Furcraea foetida. Furcreastatin consisted of hecogenin as the aglycone and a hexasaccharide containing D-galactose, L-rhamnose and four D-glucose residues. The structure was determined to be (3 beta,5 alpha,25R)- 3-hydroxyspirostan-12-one 3-O-[alpha-L-Rhap-(1-->4)-beta-D-Glcp-(1-->3)-¿beta-D-Glcp-(1-->3) -beta-D- Glcp-(1-->2)¿-beta-D-Glcp-(1-->4)-beta-D-Galp] by extensive NMR spectroscopic studies. Furcreastatin decreased the viability of mutant p53-over-expressing cells with an ED50 of 4.0 micrograms/mL, and decreased that of the parental cell-line with an ED50 of 9.6 micrograms/mL.

3T3 Cells↗
PubMed2000

Herbimycin A induces G1 arrest through accumulation of p27(Kip1) in cyclin D1-overexpressing fibroblasts.

The ansamycin antibiotic herbimycin A is a potent tyrosine kinase inhibitor and reduces the growth rate of various types of mammalian cells. When quiescent Rat6 fibroblast cells were treated with herbimycin A, serum-induced expression of cyclin D1 was inhibited, and this was associated with inhibition of G1 phase progression. However, herbimycin A also inhibited serum-induced G1 progression in derivatives of the Rat6 fibroblast cell line that stably overexpress a human cyclin D1 cDNA (R6ccnD1#4 cells), without affecting the expression levels of G1 cyclins. We found that herbimycin A prevented serum-induced downregulation of the cyclin-dependent kinase inhibitor p27(Kip1), thereby leading to inactivation of the protein kinase activity of CDK2. These results suggest that herbimycin A inhibits a tyrosine kinase(s) that plays a role in degradation of the p27(Kop1) protein.

Animals↗
PubMed2000

Inhibition of acidic sphingomyelinase by xanthone compounds isolated from Garcinia speciosa.

Sphingomyelinase is considered to be involved in the regulation of apoptosis and cell growth. In the course of our screening for acidic sphingomyelinase inhibitors we isolated three xanthone compounds, alpha-mangostin, cowanin, and cowanol, from the bark of Garcinia speciosa. These compounds competitively inhibited bovine brain-derived acidic sphingomyelinase with IC(50) values of 14.1, 19.2, and 10.9 microM, respectively and inhibited the acidic sphingomyelinase more effectively than the neutral sphingomyelinase of bovine brain. alpha-Mangostin inhibited the acidic sphingomyelinase in the most selective manner. alpha-Mangostin was chemically modified and its structure-activity relationships are discussed.

4-Chloro-7-nitrobenzofurazan↗
PubMed2000

Aminoguanidine induces haematuria of non-glomerular origin in spontaneously hypertensive rats.

BACKGROUND: Administration of N(G)-nitro-L-arginine methyl ester (L-NAME), a non-selective inhibitor of nitric oxide synthase (NOS), induces glomerulosclerosis in spontaneously hypertensive rats (SHR). We investigated the effects of administering aminoguanidine (AG), a selective inhibitor of inducible NOS (iNOS), on glomerular histology, serum creatinine concentration, albuminuria and haematuria in SHR. METHODS: SHR and Wistar Kyoto rats (WKR) (age, 7 weeks) were given a daily water supply with or without 0.1% AG. Every 4 weeks, 24 h urine samples were collected and checked for haematuria by a dipstick method, and systolic blood pressure was measured. After 16 weeks, serum creatinine, albuminuria and glomerulosclerosis indices (GSI) were evaluated, and the size of urinary erythrocytes in AG-treated SHR was measured by flow cytometry. Glomeruli were observed by transmission and scanning electron microscopy. Some AG-treated SHR received a furosemide injection and then urinary erythrocyte size was determined. RESULTS: Systolic blood pressure, serum creatinine, albuminuria and GSI were similar between the untreated and AG-treated groups in both strains. However, AG treatment induced significant haematuria in SHR, but not in WKR. Electron microscopy did not provide any evidence for glomerular bleeding sites in AG-treated SHR. In urine with osmolalities exceeding 750 mOsm/kg, haematuria of AG-treated SHR consisted of erythrocytes smaller in size than venous erythrocytes. After furosemide injection leading to near isotonic urine, the size of urinary erythrocytes was similar to that of venous erythrocytes. CONCLUSIONS: The absence of morphological evidence for glomerular bleeding sites and similar intrinsic size between urinary and venous erythrocytes suggest that AG induces a non-glomerular type of haematuria in SHR.

Albuminuria↗
PubMed2000

Differential behavior of VEGF receptor expression and response to TNP-470 in two immortalized human endothelial cell lines.

Angiogenesis consists of endothelial cell proliferation, migration and tube formation. It is useful to investigate endothelial cell behavior using immortalized endothelial cell lines. We characterized cell growth property, growth factor dependency and response to angioinhibitory drugs; TNP-470, staurosporine, radicicol and genistein, using human umbilical vein endothelial cells (HUVECs) immortalized by human papilloma virus (HPV)-16 E6-E7, named HUVECs/E6-E7, and HUVECs/E6-E7 transformed by v-Ki-ras gene, named HUVECs/E6-E7/ras. The dependency to vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor (bFGF) for cell proliferation decreased in HUVECs/E6-E7, but were restored in HUVECs/E6-E7/ras. Flow cytometric analysis demonstrated that a VEGF receptor KDR/flk-1 was down-regulated in HUVECs/E6-E7 but not in HUVECs/E6-E7/ras. Expression of another VEGF receptor flt-1 was consistent in all cells including HUVECs, HUVECs/E6-E7 and HUVECs/E6-E7/ras. According to the analysis of the angioinhibitory drugs, HUVECs/E6-E7 was obviously resistant to TNP-470, but HUVECs/E6-E7/ras showed similar response compared to HUVECs which suggests that v-Ki-ras signaling pathway is associated with VEGF receptor expression and make HUVECs/E6-E7 sensitive to TNP-470 by modulating the signal transduction cascade. In conclusion, HPV-16 E6-E7 and v-Ki-ras genes have unique growth properties and these immortalized cells are useful for investigating signal transduction pathways of endothelial cells, and for screening of angioinhibitory drugs.

Angiogenesis Inhibitors↗
PubMed2000

Naturally occurring and synthetic inhibitors of NF-kappaB functions.

Nuclear factor (NF)-kappaB is a transcription factor that induces the immunoglobulin kappa chain, cytokines such as interleukin (IL)-1, IL-2, IL-6, IL-8, tumor necrosis factor (TNF)-alpha and interferon gamma, and cell adhesion proteins. It also induces anti-apoptotic proteins, and inhibits TNF-alpha and anticancer drug-induced apoptosis. Therefore, NF-kappaB function inhibitors may be useful as anti-inflammatory and anticancer agents. Microbial products such as panepoxydone, cycloepoxydon and gliotoxin are known to inhibit activation of NF-kappaB. We have designed and synthesized new NF-kappaB inhibitors from the structure of an antibiotic, epoxyquinomicin C. The designed compound, DHM2EQ, inhibited TNF-alpha-induced activation of NF-kappaB and showed a therapeutic effect in mouse rheumatoid arthritis model.

Animals↗
PubMed1999

Molecular cloning of newt sex pheromone precursor cDNAs: evidence for the existence of species-specific forms of pheromones.

Cloning of cDNA encoding a decapeptide pheromone (sodefrin) that attracts conspecific female newts was attempted. A cDNA clone encoding a protein consisting of 189 amino acid residues including a sodefrin sequence was isolated from a Cynops pyrrhogaster abdominal gland cDNA library. Likewise, a cDNA clone encoding a molecule comparable to the sodefrin precursor was obtained from a Cynops ensicauda abdominal gland cDNA library. This clone encoded a precursor protein of 192 amino acid residues, including a sodefrin-like peptide sequence with substitutions of two amino acid residues. This is the first report of a peptide pheromone precursor in vertebrates.

Abdomen↗
PubMed1999

Stimulation of ultraviolet-induced apoptosis of human fibroblast UVr-1 cells by tyrosine kinase inhibitors.

Damnacanthal is an anthraquinone compound isolated from the root of Morinda citrifolia and was reported to have a potent inhibitory activity towards tyrosine kinases such as Lck, Src, Lyn and EGF receptor. In the present study, we have examined the effects of damnacanthal on ultraviolet ray-induced apoptosis in ultraviolet-resistant human UVr-1 cells. When the cells were treated with damnacanthal prior to ultraviolet irradiation, DNA fragmentation was more pronounced as compared to the case of ultraviolet irradiation alone. The other tyrosine kinase inhibitors, herbimycin A and genistein, also caused similar effects on ultraviolet-induced apoptosis but to a lesser extent. Serine/threonine kinase inhibitors, K252a, staurosporine and GF109203X, rather suppressed the ultraviolet-induced DNA cleavage. Immunoblot analysis showed that pretreatment with damnacanthal followed by ultraviolet irradiation increased the levels of phosphorylated extracellular signal-regulated kinases and stress-activated protein kinases. However, the other tyrosine kinase inhibitors did not increase the phosphorylation of extracellular signal-regulated kinases but stimulated phosphorylation of stress-activated protein kinases. Consequently, the ultraviolet-induced concurrent increase in both phosphorylated extracellular signal-regulated kinases and stress-activated protein kinases after pretreatment with damnacanthal might be characteristically related to the stimulatory effect of damnacanthal on ultraviolet-induced apoptosis.

Anthraquinones↗
PubMed1999

Surgical treatment of pineal region tumours through the occipital transtentorial approach: evaluation of the effectiveness of intra-operative micro-endoscopy combined with neuronavigation.

OBJECT: To determine the efficacy and accuracy of surgically-assisted systems including endoscopy combined with neuronavigation in the treatment of pineal region tumours through the occipital transtentorial approach, an evaluation of thirty-one patients undergoing surgery was performed over a 10-year period. METHOD: The study was performed in 2 parts. The surgical approach to the pineal region was the same in the two parts, but in part 2 a smaller craniotomy window was used. Part 1 (from March 1989 to March 1997) included 15 patients who underwent surgical removal of pineal region tumours without using assisted systems; four out of the fifteen patients had surgery-related complications, including seizure and hemianopsia. Part 2 (from April 1997 to February 1999) included 16 patients who underwent surgical treatment by the same surgical team and with assisted systems; all 16 patients had excellent outcomes, with no complications. CONCLUSIONS: Although this study was the first specifically to examine the efficacy of endoscopy combined with neuronavigation in the treatment of pineal region tumours, our findings suggest that these systems are very useful, safe, and accurate in evaluating the primary tumour and surrounding anatomy as well as in determining operative strategy, such as the location and size of the scalp incision, craniotomy, and the extent of surgical removal. Therefore, we conclude that the addition of endoscopy combined with neuronavigation to standard surgical procedures can improve the outcome of surgical treatment of pineal region tumours.

Adolescent↗
PubMed1999

Screening for inducers of apoptosis in apoptosis-resistant human carcinoma cells.

Many anticancer agents are known to induce apoptosis in cultured cells, but human solid tumor cells are often resistant to apoptosis induction. Human pancreatic adenocarcinoma AsPC-1 cells were found to be resistant to apoptosis. So, we screened microbial culture filtrates and synthetic chemicals for their ability to induce apoptosis in AsPC-1 cells. Polyoxypeptin A was isolated from a Streptomyces culture broth as a potent inducer of apoptosis. Its cyclic hexadepsipeptide structure contains a simple but hitherto unreported amino acid, (2S,3R)-3-hydroxy-3-methylproline. Polyoxypeptin A induced early cell death, apoptotic morphology, and internucleosomal DNA fragmentation in AsPC-1 cells at low concentrations. Polyoxypeptin A can induce caspase 3 activation in human T cell leukemia Jurkat cells but not in AsPC-1 cells. The mechanism of apoptosis in AsPC-1 cells has not been elucidated yet. Less toxic derivatives of polyoxypeptin A are being prepared. A macrocyclic lactam called BE-14106 was also isolated from Streptomyces as an inducer of apoptosis in AsPC-1 cells. Histidine-pyridine-histidine-3 (HPH-3) is an oxygen-activating ligand derived from the structure of bleomycin, and it also induced apoptosis in AsPC-1 cells. Induction of apoptosis by HPH-3 was inhibited by zinc and copper ions, indicating that chelation with ferrous ion is responsible for induction of apoptosis, as is chelation by bleomycin to cleave DNA. Bleomycin A2 and its portion having no DNA-binding region, glycopeptide-3(GP-3), did not induce apoptosis in AsPC-1 cells. Thus, among the actions of bleomycin-related compounds, the induction of apoptosis is a unique characteristic of HPH-3.

Anti-Bacterial Agents↗
PubMed1999

Coexistence of intracranial arteriovenous malformation with Turcot's syndrome: a case report.

Turcot's syndrome is a combination of multiple adenomatous gastrointestinal polyps and neuroepithelial tumors of the central nervous system (CNS). A 16-year-old man presented with Turcot's syndrome consisting of nonfamilial colorectal polyposis and multiple fibrillary astrocytomas accompanied by ruptured intracranial arteriovenous malformation (AVM) manifesting as generalized epileptic activity. Multiple CNS tumors are extremely unusual in Turcot's syndrome. This is the first description of Turcot's syndrome associated with an intracranial AVM. This case may correspond to a new phenotypic variant of colonic polyposis syndrome.

Adenomatous Polyposis Coli↗
PubMed1998

Requirement of caspase-3(-like) protease-mediated hydrogen peroxide production for apoptosis induced by various anticancer drugs.

Caspase-3(-like) proteases play important roles in controlling mammalian apoptosis. However, the downstream events from the caspase-3(-like) protease activation to death of cells are still unclear. Previously, we reported that hydrogen peroxide (H2O2) was generated by the activation of caspase-3(-like) proteases in the process of tyrosine kinase inhibitor-induced apoptosis in human small cell lung carcinoma Ms-1 cells. In the present study, we examined whether generation of H2O2 is a critical event for the apoptotic pathway downstream of caspase-3(-like) protease activation by various anticancer drugs. Anticancer drugs such as camptothecin, vinblastine, inostamycin, and adriamycin induced activation of caspase-3(-like) proteases and apoptosis. Generation of H2O2 was commonly detected after treatment with each of the four anticancer drugs, and scavenging of H2O2 caused cells to fail to undergo apoptosis. Moreover, anticancer drug-induced H2O2 production was inhibited not only by an inhibitor of caspase-3(-like) proteases but also by diphenyleneiodonium chloride, an inhibitor of flavonoid-containing enzymes such as NADPH oxidase. However, activation of caspase-3(-like) proteases was not inhibited by diphenyleneiodonium chloride. These findings suggest that activation of caspase-3(-like) proteases by various anticancer drugs causes generation of H2O2 presumably through the activation of NADPH oxidase, thereby inducing apoptosis. Therefore, H2O2 may function as a common mediator for apoptosis induced by various anticancer drugs.

Acetylcysteine↗