Biomedical subjects

Y Saito

Publications and source records attributed to Y Saito.

At least 127 records · Page 7Linked to original sources

PubMed2001

Synthesis of isotopically labeled D-[1'-13C]ribonucleoside phosphoramidites.

The preparation of fully protected labeled diisopropylamino-beta-cyanoethyl-[1'-13C]ribonucleoside phosphoramidites with regioisomeric purity is described. We demonstrated in this paper that a regioselective 2'-O-silylation, through a 3',5'-O-di-tert-butylsilanediyl protection, has been applied for the synthesis of [1'-13C]ribonucleoside phosphoramidite units. This method allowed us to obtain only the desired 2'-O-silyl-3'-O-phosphoramidites avoiding the undesired 3'-O-silyl-2'-O-phosphoramidite nucleosides isolated by standard procedures. This is a suitable procedure to RNA precursors with respect to the isotope-containing precursors.

Carbon Isotopes↗

PubMed2001

Structure-antimutagenic activity relationships of benzalacetone derivatives against UV-induced mutagenesis in E. coli WP2uvrA and gamma-induced mutagenesis in Salmonella typhimurium TA2638.

The antimutagenic activities of benzalacetone (4-phenyl-3-buten-2-one) and its structurally-related compounds were evaluated through their use as post-treatments for the UV-induced mutagenesis in Escherichia coli WP2s (uvrA) and the gamma-induced mutagenesis in Salmonella typhimurium TA2638, the latter of which is sensitive to oxidants. Structure-activity relationships were studied between IC(50) activity values, i.e. the dose (micromol/ml) at which the mutation frequency is reduced to 50% of the control, and electronic and hydrophobicity properties of the studied molecules. Benzalacetone and benzalacetone analogs, cinnamaldehyde and trans-1,1,1-trifluoro-4-phenyl-3-buten-2-one (TF), inhibited both forms of mutagenesis, but methyl cinnamate, cinnamic acid and cinnamamide did not. The IC(50) values of TF, for UV-induced mutagenesis and gamma-induced mutagenesis, were 0.028 and 0.045 micromol/ml, respectively, and one order of magnitude lower than those of cinnamaldehyde and benzalacetone. The three antimutagenic analogs listed in order of decreasing activity are: TF>>cinnamaldehyde>benzalacetone. This order is proportional to the electron-withdrawing property of the terminal group attached to an alpha,beta-unsaturated carbonyl moiety in the side chain that is known to play an important role in the antimutagenicities of benzalacetone and related compounds. In UV-induced mutagenesis in E. coli WP2s, mono-substituted benzalacetones - the ring-substituents of which have electron-withdrawing properties - showed antimutagenic activity that correlated with their electronic property. In gamma-induced mutagenesis in S. typhimurium TA2638, the antimutagenic activities of mono-substituted benzalacetones were proportional to the substituent hydrophobicities (pi). The different effects on both the mutation-induced systems is suggested to be related to the relative permeability of the cell membranes and the different sensitivities to mutagens between E. coli WP2s and S. typhimurium TA2638. In addition, the antimutagenic activity against gamma-induced mutagenesis could be due to the ability of parent compounds or their derivatives to scavenge long-lived organic radicals; the radicals have been described to be generated as a result of the X-irradiation of cells by Koyama et al. [Mutat. Res. 421 (1998) 45].

Antimutagenic Agents↗

PubMed2001

Hemispheric lateralization in the cortical motor preparation for human vocalization.

To investigate the cortical information processing during the preparation of vocalization, we performed transcranial magnetic stimulation (TMS) over the cortex while the subjects prepared to produce voice in response to a visual cue. The control reaction time (RT) of vocalization without TMS was 250-350 msec. TMS prolonged RT when it was delivered up to 150-200 msec before the expected onset of voice (EOV). The largest delay of RT was induced bilaterally over points 6 cm to the left and right of the vertex (the left and right motor areas), resulting in 10-20% prolongation of RT. During the early phase of prevocalization period (50-100 msec before EOV), the delay induced over the left motor area was slightly larger than that induced over the right motor area, whereas, during the late phase (0-50 msec before EOV), it was significantly larger over the right motor area. Bilateral and simultaneous TMS of the left and right motor areas induced delays not significantly different from that induced by unilateral TMS during the early phase, but induced a large delay well in excess of the latter during the late phase. Thus, during the cortical preparation for human vocalization, alternation of hemispheric lateralization takes place between the bilateral motor cortices near the facial motor representations, with mild left hemispheric predominance at the early phase switching over to robust right hemispheric predominance during the late phase. Our results also suggested involvement of the motor representation of respiratory muscles and also of supplementary motor cortex.

Adult↗

PubMed2001

Effect of apolipoprotein E3/4 phenotype on postprandial triglycerides and retinyl palmitate metabolism in plasma from hyperlipidemic subjects in Japan.

In a previous study it was shown that postprandial lipid metabolism is delayed in individuals with intra-abdominal visceral fat accumulation. Population studies have shown that as compared with individuals with apolipoprotein (apo) E3/3, those with phenotype apo E3/4 phenotype have higher plasma and low density lipoprotein (LDL)-cholesterol (C) concentration and increased susceptibility to coronary heart disease. The aim of the present study is to determine how apo E4 affects postprandial lipid metabolism by comparing individuals with apo E3/4 to those with apo E3/3 phenotype matched for abdominal visceral fat. Sixty-two Japanese subjects (41 male, 21 female) [average age 48+/-14 years; mean body mass index (BMI) 25+/-5.6 kg/m2] were recruited for this study. The subjects were divided into two groups: those with apo E3/3 (n=43) and those with apo E3/4 phenotype (n=19), as determined by isoelectric focusing (IEF). Visceral fat accumulation was analyzed as area of fat deposition by computerized tomography at the umbilicus level. After a 12-h overnight fasting, an oral vitamin A and a fatty meal were administered to these subjects. The plasma triglyceride (TG) increased significantly hours after fat loading in both groups but the levels of TG were significantly higher in apo E3/4 than in apo E3/3 phenotype at 2, 4 and 6 h after fat loading. Plasma retinyl palmitate (RP) levels were also significantly higher in individuals with apo E3/4 than in those with apo E3/3 phenotype at 2, 4 and 6 h after fat loading. This investigation was then conducted in both genders separately, and found that these associations were statistically significant in men. Furthermore, after matching men for fasting TG levels, these associations did not persist for plasma TG levels at any time point, while plasma RP levels were still significantly higher in apo E3/4 group at 2 and 6 h after fat loading. These results indicate that in Japanese population especially for men apo E phenotype E3/4 is associated with an impaired postprandial TG-rich lipoprotein metabolism relative to apo E3/3 phenotype when matched for intra-abdominal visceral fat accumulation, which has a substantial effect on the metabolism of plasma TG-rich lipoproteins.

Adult↗

PubMed2001

Mesenchymal transcription factor Fkh6 is essential for the development and differentiation of parietal cells.

The role of transcription factor forkhead homologue 6 (Fkh6) gene expressed only in gastrointestinal mesenchymes on the differentiation of gastric epithelia was analyzed by inactivating the gene by targeting disruption. Gastric mucosa exhibited hyperplasias with disordered glandular structures in the absence of gene. Measurement of acid secretion in the isolated whole stomach demonstrated that both basal and stimulated secretions were severely suppressed in the Fkh6-/- stomach, while immunohistochemical studies showed that comparable numbers of parietal cells were differentiated in both wild-type and Fkh6-/- stomachs. Ultrastructurally Fkh6-/- parietal cells were furnished with developed intracellular canaliculi and many mitochondria, but their canaluculi were not enlarged nor fully connected to the luminal surface even when animals were treated with histamine, suggesting that Fkh6-/- parietal cells were far less responsive to acid secretion-inducing stimulations. Some parietal cells contained secretory granules positively stained with anti-pepsinogen antibodies, indicating that they retained characteristics of oxynticopeptic cells found in lower vertebrates. We thus concluded that Fkh6 plays essential roles for the development and differentiation of parietal cells via epithelial-mesenchymal interactions.

Animals↗

PubMed2001

Oncostatin M promotes biphasic tissue factor expression in smooth muscle cells: evidence for Erk-1/2 activation.

Tissue factor (TF), a transmembrane glycoprotein, initiates the extrinsic coagulation cascade. TF is known to play a major role in mediating thrombosis and thrombotic episodes associated with the progression of atherosclerosis. Macrophages at inflammatory sites, such as atherosclerotic lesions, release numerous cytokines that are capable of modulating TF expression. This study examined the role of oncostatin M (OSM), a macrophage/ T-lymphocyte-restricted cytokine, in the expression of TF in vascular smooth muscle cells (SMCs). It is reported here that OSM stimulated a biphasic and sustained pattern of TF messenger RNA (mRNA). The effect of OSM on TF mRNA expression was regulated at the transcriptional level as determined by nuclear run-offs and transient transfection of a TF promoter-reporter gene construct. OSM-induced TF expression was regulated primarily by the transcription factor NF-kappaB. Activation of NF-kappaB by OSM did not require IkappaB-alpha degradation. Inhibition of MEK activity by U0126 prevented OSM-induced TF expression by suppressing NF-kappaB DNA binding activity as determined by gel-shift analysis. Further, inhibition of Erk-1/2 protein by antisense treatment resulted in suppression of TF mRNA expression, indicating a role for Erk-1/2 in modulating NF-kappaB DNA binding activity. These studies suggest that the induced expression of TF by OSM is primarily through the activation of NF-kappaB and that activation of NF-kappaB is regulated in part by the MEK/Erk-1/2 signal transduction pathway. This study indicates that OSM may play a key role in promoting TF expression in SMCs within atherosclerotic lesions.

Blood Coagulation↗

PubMed2001

Maxadilan specifically interacts with PAC1 receptor, which is a dominant form of PACAP/VIP family receptors in cultured rat cortical neurons.

Maxadilan is a potent vasodilator peptide isolated from salivary gland extracts of the hematophagous sand fly. Recently, the possibility was demonstrated that maxadilan binds to PAC1 receptor (PACAP, pituitary adenylate cyclase activating polypeptide type I receptor) in mammals. In the present study, we demonstrated that: (1) maxadilan specifically binds to PAC1 receptor and stimulates cyclic AMP accumulation in a dose-dependent manner in CHO cells stably expressing PAC1 receptor, not VIP (vasoactive intestinal polypeptide) receptors; that (2) the deleted peptide (amino acid #24-42) of maxadilan (termed max.d.4) also specifically binds to PAC1 receptor although max.d.4 inhibits cyclic AMP accumulation stimulated by both maxadilan and PACAP; and that (3) max.d.4 completely blocks the cyclic AMP accumulation induced by VIP in cultured rat cortical neurons. The expression of specific PACAP receptors in cultured rat cortical neurons was further investigated by the reverse transcription-polymerase chain reaction technique, which showed the presence of mRNA coding for PAC1 receptor among PACAP/VIP family receptors. These data indicate that maxadilan and max.d.4 represent important tools for clarifying the physiological role of PAC1 receptor, and that PAC1 receptor plays an important role in the regulation of the functions induced by PACAP in rat cultured cortical neurons.

Amino Acid Sequence↗

PubMed2001

Diet-induced hyperhomocysteinemia exacerbates neointima formation in rat carotid arteries after balloon injury.

BACKGROUND: Increasing evidence indicates that elevated plasma homocysteine levels are associated with an increased risk of atherosclerosis and endothelial dysfunction, although little specific information on the mechanisms responsible for the atherogenic effects of homocysteine or on the in vivo contribution made by hyperhomocysteinemia to atherosclerosis is currently available. Because homocysteine is known to exert a direct inhibitory effect on endothelial cell growth in vitro, we hypothesized that this effect contributes to the progression of atherosclerotic lesions initiated by endothelial damage caused by mechanical injury. METHODS AND RESULTS: We prepared diet-induced hyperhomocysteinemic rats in which neointima formation after balloon injury to the common carotid artery was assessed. Moderate hyperhomocysteinemia (plasma homocysteine levels 3- to 4-fold higher than control) significantly exacerbated neointima formation. Oral administration of folate, which had a homocysteine-lowering effect, diminished neointima formation induced by moderate hyperhomocysteinemia. Furthermore, the attenuation of reendothelialization was shown in diet-induced hyperhomocysteinemic rats with Evans blue staining. CONCLUSIONS: Diet-induced hyperhomocysteinemia, even mild to moderate, exacerbates neointima formation after denuding injury, making hyperhomocysteinemia a likely risk factor for postangioplasty restenosis. It may be mediated through an inhibitory effect of homocysteine on reendothelialization. Homocysteine lowering with folate supplementation can effectively ameliorate the detrimental effects of moderate hyperhomocysteinemia. Clinical trials would seem to be warranted.

Administration, Oral↗

PubMed2001

Aldosterone production is activated in failing ventricle in humans.

BACKGROUND: Recent reports have indicated that aldosterone is produced in extra-adrenal tissues in animals. The present study was designed to examine whether aldosterone is produced in human heart. METHODS AND RESULTS: Plasma levels of aldosterone, BNP, and angiotensin-converting enzyme were measured in anterior interventricular vein (AIV), coronary sinus (CS), and aortic root (Ao), respectively, in 20 patients with left ventricular systolic dysfunction (LVSD), 25 patients with LV diastolic dysfunction (LVDD), and 23 control subjects. Aldosterone levels were significantly higher in AIV and CS than Ao in LVSD (98+/-10 versus 72+/-9 pg/mL, P:<0.001, and 97+/-11 versus 72+/-9 pg/mL, P:<0.001, respectively) and LVDD (87+/-10 versus 71+/-9 pg/mL, P:<0.01, and 84+/-10 versus 71+/-9 pg/mL, P:<0.01, respectively) groups, but no differences were observed in levels for these sites in the control group. Levels of ACE activity and BNP also were higher in AIV than Ao in both LV dysfunction groups. The difference in aldosterone levels between AIV and Ao and those in BNP and angiotensin-converting enzyme had a significant positive correlation with LVEDP and a significant negative correlation with LV ejection fraction in the LVSD group. CONCLUSIONS: Production of aldosterone, angiotensin-converting enzyme, and BNP are activated in failing human ventricle in proportion to severity.

Adult↗

PubMed2001

Capillary electrochromatography using fibers as stationary phases.

Fiber-packed capillary columns have been evaluated in chromatographic performance in capillary electrochromatography (CEC). The change of electroosmotic flow (EOF) velocity and selectivity using different kinds of fiber materials was examined. Although the EOF velocity among the different fiber packed columns was almost the same, retention of parabens was larger on the Kevlar-packed column than on the Zylon-packed one, and was larger on the as-span-type fiber-packed column than on the high-modulus-type packed one. Using 200 microm ID x 5 cm Kevlar packed column combined with a 100 microm ID x 20 cm precolumn capillary and a 530 microm ID x 45 cm postcolumn capillary, the separation of three parabens within 30 s was achieved. Other compounds were also separated in a few minutes by the fiber-packed CEC method.

Electrophoresis, Capillary↗

PubMed2001

Sample preparation with fiber-in-tube solid-phase microextraction for capillary electrophoretic separation of tricyclic antidepressant drugs in human urine.

Solid-phase microextraction (SPME) is a solvent-free sample preparation technique using a thin coating attached to the surface of a fused silica-fiber as the extraction medium, which has been successfully applied to the analysis of a wide variety of compounds by coupling to gas chromatography (GC). In recent years, in-tube SPME using GC capillary column as the extraction medium has also been developed and coupled with liquid chromatography (LC) for the preconcentration of nonvolatile compounds. In this study, an on-line interface between the fiber-in-tube SPME and capillary electrophoresis (CE) has been developed, and the preconcentration and separation of four tricyclic antidepressant (TCA) drugs, amitriptyline, imipramine, nortriptyline, and desipramine, were performed with the hyphenated system. Under the optimized condition, a better extraction performance than conventional in-tube SPME was obtained, even the length of the extraction medium was much shorter. The results clearly indicated that the fiber was working effectively as an extraction medium. For the separation of these four TCAs, capillary electrophoretic separation with beta-cyclodextrin as the buffer additive has been employed and the application of the developed system to the analysis of complex sample mixtures in a biological matrix is also demonstrated.

Amitriptyline↗

PubMed2001

Interferon regulatory factor 1 promoter polymorphism and response to type 1 interferon.

The clinical success of interferon-treatment has been found to vary in different individuals. To explain this, we hypothesized that responses to type 1 interferons could be partly determined by interferon regulatory factor-1 gene transcription, because the latter is an important transcription factor in the interferon system. We demonstrated that the antiproliferative effect of type 1 interferons on human liver cancer cells correlates with levels of transcription of the interferon regulatory factor-1 gene in parallel with those of p21(WAF-1) expression. Here, we investigated whether mutations in the interferon regulatory factor-1 gene cause different responses to type 1 interferons. DNA from several human liver cancer cell lines and peripheral blood mononuclear cells was investigated. Nucleotide sequences of the interferon regulatory factor-1 gene and polymerase chain reaction products of its upstream region were determined directly and after cloning. The promoter activity of the upstream region of this gene was measured by the luciferase reporter assay. We found 4 point mutations in the upstream (- 1 approximately - 495) region, and the luciferase promoter assay demonstrated that these mutations did modify promoter activity. Analysis of DNA from healthy volunteers showed that these mutations are single nucleotide polymorphisms. These results suggest that single nucleotide polymorphisms of the interferon regulatory factor-1 promoter contribute, at least in part, to determining responses to type 1 interferons. J. Cell. Biochem. Suppl. 36: 191-200, 2001.

Antineoplastic Agents↗

PubMed2001

Reduction of telomerase activity in human liver cancer cells by a histone deacetylase inhibitor.

The presence of telomerase has been demonstrated recently in many different malignancies. Several reports documented that in human hepatocellular carcinoma, the level of telomerase activity parallels its differentiation stage. In the present study, the effect of the differentiation-inducing agent sodium butyrate on telomerase activity in four human liver cancer cell lines was investigated using the telomeric repeat amplification protocol. We assayed telomerase activity before and after butyrate treatment and in cell cycle synchronized non-dividing quiescent cells. In addition, telomerase reverse transcriptase levels were measured at the mRNA level. All four cell lines possessed high but not identical levels of telomerase activity. Telomerase activity was significantly reduced by treatment with sodium butyrate as well as trichostatin A in a dose- and time-dependent fashion, paralleling the reduction of cell proliferation. Although methotrexate, hydroxyurea, and colchicine synchronized the cell cycle at G1, S, and G2/M, respectively, and thereby also caused proliferating cells to cease dividing and become quiescent, in this case telomerase activity remained essentially unaltered compared to the control cultures. Moreover, levels of mRNA encoding telomerase reverse transcriptase were not always significantly altered by either sodium butyrate treatment or cell cycle synchronization. These results suggest that sodium butyrate, as a histone deacetylase inhibitor, effectively reduces telomerase activity without affecting transcription levels of the reverse transcriptase component.

Antineoplastic Agents↗

PubMed2001

Expression of vascular endothelial growth factor receptors in smooth muscle cells.

Vascular Endothelial Growth Factor (VEGF) has been typically considered to be an endothelial-specific growth factor. However, it was recently demonstrated that VEGF can interact with non endothelial cells. In this study, we tested whether vascular smooth muscles cells (VSMCs) can express VEGF receptors, such as flk-1, flt-1, and neuropilin (NP)-1, and respond to VEGF in vitro. In cultured VSMCs, flk-1 and flt-1 expression was inversely related to cell density. The expression of flk-1 was down-regulated with increasing passage numbers. However, NP-1 levels were not affected by cell density or passage numbers. Flk-1, Flt-1, and NP-1 protein levels were confirmed by Western Blotting. Although the functional mature form of Flk-1 protein is expressed at low levels in VSMCs, phosphorylation of Flk-1 following VEGF(165) stimulation was still observed. SMCs migrated significantly in response to VEGF(165) and VEGF-E, whereas Placenta Growth Factor (PlGF) induced migration only at higher concentrations. Since VEGF-E is a specific activator of flk-1 while PlGF specifically activates only flt-1, SMC migration induced by VEGF(165) is likely to be mediated primarily through the flk-1 receptor. VSMCs did not significantly proliferate in response to VEGF(165), PlGF, and VEGF-E. In conclusion, our studies demonstrate the presence of VEGF receptors on VSMCs that are functional. These studies also indicate that in vivo, VEGF may play a role in modulating the response of VSMCs.

Animals↗

PubMed2001

Reduction of c-myc expression by an antisense approach under Cre/loxP switching induces apoptosis in human liver cancer cells.

c-Myc has been documented to be both a positive and a negative signal for the induction of apoptosis. It is well known that overexpression of the c-myc gene induces apoptosis of normal cells, but the result of a reduction in its expression is not fully understood. We examined whether a reduction in c-myc expression would induce apoptosis in human liver cancer cells. Specifically, antisense and sense oligodeoxynucleotides (oligos) against the human c-myc mRNA were synthesized, mixed with a liposome reagent at various ratios, and were applied to the liver cancer-derived cell lines, HCC-T, HepG2, and PLC/PRF/5. To exclude effects resulting from using oligos, plasmid vectors expressing the full-length c-myc cDNA in both sense and antisense orientations under the control of the Cre/loxP system were generated. Monoclonal cell lines including these plasmid vectors were produced and Cre was supplied by adenovirus infection. Apoptosis was determined morphologically and c-Myc and Bcl-2 expression was examined by Western blotting. The antisense myc significantly inhibited the proliferation of the cells within two days, while neither the liposome reagent alone nor sense myc did so. Most of the cells were rounded up by the antisense-treatment and nuclear fragmentation and DNA ladder formation were detected after two days in antisense c-myc-treated cells. Antisense c-myc largely reduced c-Myc and partially Bcl-2 expression; overexpression of Bcl-2 partially rescued from apoptosis in HCC-T and HepG2 cells. These results suggest that the massive reduction in c-myc mRNA induces apoptosis in liver cancer cell lines and consequent decrease in Bcl-2 enhances the cell death. c-Myc reduction under the Cre/loxP switching system may be a useful tool for the clarification of c-myc-related cellular mechanisms in differentiation and proliferation.

Apoptosis↗

PubMed2001

High sensitivity of PCR in situ hybridization for the detection of human papillomavirus infection in uterine cervical neoplasias.

OBJECTIVE: This study was designed in order to examine whether the sensitivity of PCR in situ hybridization (PISH) is superior to that of fluorescence in situ hybridization (FISH) and immunocytochemical staining (ICS) in detecting the presence of human papillomavirus (HPV) infection in uterine cervical neoplasias. METHODS: Three cell specimens were obtained from every 54 patients who had been histologically and cytologically diagnosed as severe dysplasia of the uterine cervix (SD), carcinoma in situ of the uterine cervix (CIS), or microinvasive carcinoma of the uterine cervix (MIC). All of them were first stained by the Papanicolaou (pap) method before the experiments. After specimens were classified into SD (n = 17) and CIS/MIC groups (n = 37), the sensitivities of detection for HPV infection were compared among PISH, FISH, and ICS methods which had been carried out after decolorization of the pap stain. RESULTS: In the SD group, PISH demonstrated a 58.8% positive incidence of HPV, which was significantly higher than that (23.5%) shown by FISH (P < 0.05). There was no significant difference in the positivities of HPV between the PISH and ICS (47.1%) methods. In the CIS/MIC group, PISH, FISH, and ICS showed 73.0, 43.2, and 54.1% positive incidences of HPV, respectively. There was significant difference in HPV positivities between PISH and FISH as well as ICS (P < 0.01, P < 0.05). The total frequency of the detection of HPV infection by PISH was significantly higher than that by FISH (P < 0.01) and high with a marginal significance compared to that by ICS (P = 0.051). Moreover, the morphologic change of a single cell and the HPV-positive signals could be observed simultaneously by the PISH technique. CONCLUSION: Because PISH possesses high sensitivity for the detection of HPV infection in morphologically intact cells from uterine cervical neoplasia, the PISH technique might have promising potential for application to the detection of HPV presence in situ in screening.

Carcinoma↗

PubMed2001

Effects of melatonin on the proliferation and cis-diamminedichloroplatinum (CDDP) sensitivity of cultured human ovarian cancer cells.

OBJECTIVES: In this study, we investigated the antiproliferative effect and telomerase activity of melatonin with or without cis-diamminedichloroplatinum (CDDP) on CDDP-sensitive HTOA cells and CDDP-resistant OVCAR-3 cells of cultured human ovarian cancer. METHODS: HTOA cells and OVCAR-3 cells were cultured in RPMI-1640 at 37 degrees C with 5% CO(2) for 132 h. To examine the antiproliferative effect of melatonin, cells were cultured with or without melatonin (10(-12)-10(-6) M) and thereafter counted in a 96-well microplate using the alamarBlue assay. To examine the effect of melatonin and CDDP, cells were divided into group A (intermittent CDDP, 0.5 microg/ml), group B (intermittent CDDP + melatonin), and group C (sequential (12-h interval) CDDP/melatonin) and thereafter counted in a 96-well microplate using the alamarBlue assay. In different series, cells were cultured and treated with either ethanol, melatonin, CDDP, or CDDP + melatonin. After harvest, telomerase activity was semiquantified with a fluorescence-based telomeric repeat amplification protocol (F-TRAP). RESULTS: (1) Melatonin produced no antiproliferative effect on both types of ovarian cancer cells. (2) Melatonin 10(-6) M induced the antiproliferative effect in groups B and C compared with group A in the HTOA cell line. (3) Melatonin 10(-9) M produced the antiproliferative effect in groups B and C compared with group A in the OVCAR-3 cell line. (4) Telomerase activity in the HTOA cell line did not change but, in the OVCAR-3 cell line, was significantly lower in the CDDP + melatonin group compared with the ethanol and CDDP groups. CONCLUSIONS: Melatonin enhanced CDDP sensitivity in two ovarian cancer cell lines. Thus, melatonin may improve ovarian cancer chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Transactivation: a novel signaling pathway from angiotensin II to tyrosine kinase receptors.

Angiotensin II (Ang II), an octapeptide pressor hormone, activates cellular events that may contribute to the pathogenesis of cardiovascular disease. The physiological actions of Ang II are mediated via the Ang II type 1 receptor (AT1R) and type 2 receptor (AT2R), which are G protein-coupled receptors (GPCR). GPCR share a common basic structure of seven transmembrane helices connected by alternating cytoplasmic and extracellular loops. GPCR lack intrinsic kinase activity possessed by receptor tyrosine kinases (RTK) such as platelet-derived growth factor receptor (PDGFR) or epidermal growth factor receptor (EGFR). Nonetheless, the signal transduction events activated by the AT1R mimic those of RTKs. Recently, cross-talk between GPCR and RTK has been observed. There is accumulating evidence that GPCR take advantage of signaling pathways downstream of RTK to exert its effect on the cells. In this context, RTK may be considered as one of signaling molecules downstream of GPCR.

Angiotensin II↗