Search PubMed⌕ Search

Biomedical subjects

H Oguchi

Publications and source records attributed to H Oguchi.

157 records · Page 9Linked to original sources
PubMed1977

Effects of polyamines on the degradation of ribonucleic acids by polynucleotide phosphorylase of Micrococcus luteus.

The effects of polyamines on the breakdown of synthetic polynucleotides [poly(A), poly(C), and poly(U)] by polynucleotide phosphorylase [polyribonucleotide: orthophosphate nucleotidyltransferase, EC 2.7.7.8] from Micrococcus luteus have been studied. Although the breakdown of all the synthetic polynucleotides tested was stimulated by polyamines, the degree of stimulation by polyamines was in the order poly(C) greater than poly(A) greater than poly(U) at pH 7.5. However, the difference in degree of stimulation among polynucleotides decreased as the pH or monovalent cation concentration was increased. In the presence of heparin, an inhibitor of polynucleotide phosphorylase hydrolysis of polynucleotides, spermidine clearly stimulated the breakdown of poly(C) and poly(A), while the breakdown of poly(U) was stimulated only slightly by the addition of spermidine. Although binding of [14C]spermine to polynucleotide phosphorylase was observed by gel filtration, the amount of spermine bound to the enzyme was much less than that to RNA.

Binding Sites↗
PubMed1975

In vitro studies of bone resorption by the root-resorbing tissue from the bovine deciduous tooth.

Granulation tissue which is responsible for root resorption of deciduous tooth lies between root of the deciduous tooth and its permanent tooth germ. This tissue is called "root-resorbing tissue". Its bone-resorbing activity was investigated in vitro. Bovine root-resorbing tissue was cultured in close contact with 45Ca-labeled dead calvaria of rats. Bone-resorbing activity was determined by measuring 45Ca released from labeled calvaria during culture. It was found that only the root-resorbing tissue which was rich in odontoclasts and had a good blood supply in its surface layer had bone-resorbing ability, and that bone resorption occurred only when it was placed in close contact with calvarium. The root-resorbing tissue which was poor in odontoclasts and blood vessels failed to stimulate by 25-hydroxy-vitaim D3 or heparin, but not by larger amounts of parathyroid hormone, vitamin D3, and dihydrotachysterol when added to the culture.

Alveolar Process↗
PubMedDate not supplied

Over-etching effects on micro-tensile bond strength and failure patterns for two dentin bonding systems.

OBJECTIVES: The purpose of this study was to determine (1) the weakest zone of resin-dentin bonds and (2) the relation between bond strength and failure mode to clarify the effect of demineralized dentin. METHODS: Human premolars were sectioned to expose the dentin surfaces, and the dentin surfaces were conditioned with phosphoric acid for 15, 60, 120, or 180s. Resin-dentin bonded specimens were produced using two adhesives: One-Step (Bisco) and OptiBond Solo (Kerr). Each sample was sectioned to produce a beam (adhesive area: 0.9mm(2)). Microtensile bond tests were then conducted, and the mean bond strengths (n=12 for each group) were statistically compared using two-way ANOVA and Duncan's multiple-range test (p<0.05). The fractured surfaces of all specimens were examined using SEM, and the areas of failure were measured using an image analyzer. RESULTS: For One-Step, the bond strength decreased with increase in acid-conditioning time (15s: 50.7+/-9.7, 60s: 40.8+/-11.0, 120s: 23.6+/-4.9 and 180s: 12.1+/-4.6MPa) (p<0.05). For OptiBond Solo, the bond strength in the case of 15s acid-conditioning time (42.6+/-7.9MPa) was significantly greater than that for the other times (60s: 31.9+/-10.3, 120s: 31.8+/-14.4 and 180s: 31.8+/-7.4MPa) (p<0.05). Fractography showed that the area percentage of the hybrid layer increased with increase in etching time for both systems. CONCLUSIONS: The integrity of the hybrid layer, especially the top part, has an effect on bond strength.

Acid Etching, Dental↗
PubMedDate not supplied

Plasma human atrial natriuretic peptide levels in patients with liver cirrhosis.

Plasma levels of human atrial natriuretic peptide (hANP) were investigated in patients with liver cirrhosis, and the relationships between plasma hANP levels and the following factors were studied: presence of ascites, serum and urine electrolytes, plasma renin activity, angiotensin I and II, aldosterone, catecholamines, prostaglandin derivatives, conventional liver function tests and circulating blood volume. Plasma hANP level was significantly (P less than 0.05) elevated in patients with ascites (mean = 58.6 pg/mL, s.e.m. = 8.8) compared with cases without ascites (mean = 36.6 pg/mL, s.e.m. = 2.6). With the disappearance of ascites, the level fell to normal in most cases. Urine sodium excretion was positively correlated with plasma hANP in patients without ascites, but not in patients with ascites. The plasma hANP level was disproportionately high for the rate of urinary Na excretion in cirrhotics with ascites. The plasma hANP level was not correlated with any of the other factors such as blood volume, renin-angiotensin-aldosterone levels, catecholamines and liver function tests. These results suggest that plasma hANP levels are elevated in cirrhotic patients especially with ascites, but the natriuretic response of the kidney to this raised hANP level can be impaired in patients with liver cirrhosis and ascites.

Ascites↗
PubMedDate not supplied

Positive correlation between cytochrome P450 2E1 mRNA level and serum estradiol level in human uterine endometrium.

Most carcinogens are bioactivated by cytochrome P450s (CYPs) and these enzymes within target cells are closely related to susceptibility to cancer. Since extrahepatic CYPs occur typically at much lower levels, the existence and the role of CYP in extrahepatic tissues have been difficult to assess. In this study, we modified the reverse transcriptase-polymerase chain reaction (RT-PCR) to evaluate the relative quantities of CYP 2E1 mRNA in human endometrium. Total RNA from human endometrium was reverse-transcribed and co-amplified by PCR in the same tube containing both primer pairs of CYP 2E1 and beta-actin. The CYP 2E1 and beta-actin PCR products were 298 and 600 bp, respectively. The restriction enzyme MboI digested these two products to the predicted size for DNA fragments, demonstrating that both PCR products were specific and CYP 2E1 mRNA exists in human endometrium. CYP 1A1 mRNA was also examined, but could not be detected clearly. Adding [alpha-32P]dCTP to the reaction mixture made it possible to quantify the relative yield of the CYP 2E1 PCR product in comparison with the beta-actin product. The ratio of the yield of the CYP 2E1 PCR product to the beta-actin PCR product could be calculated at a point of 25 cycles of amplification. This ratio and serum estradiol levels were correlated positively (r = 0.654; p < 0.05), but no relationship to serum progesterone levels was observed.

Adult↗
PubMedDate not supplied

Glutathione related enzymes in cis-diamminedichloroplatinum (II)-sensitive and-resistant human ovarian carcinoma cells.

A cis-diamminedichloroplatinum (II) (CDDP)-resistant cell line (NOS2CR) demonstrated 7.4-fold greater resistance to CDDP compared with the parental cell line (NOS2) established from a patient with serous cystadenocarcinoma of the ovary. We investigated the role of enzyme systems associated with glutathione (GSH) in these cell lines. The GSH content was almost identical in both cell lines. Preincubation with 50 microM DL-buthionine-S, R-sulfoximine (BSO), an inhibitor of gamma-glutamyl cysteine synthetase, for 24 hr reduced the IC50 in both NOS2 and NOS2CR cells. Glutathione-S-transferase pi (GST-pi) activity and mRNA level in NOS2CR cells were higher than in NOS2 cells. However, gamma-glutamyltranspeptidase (GGT) activity in NOS2CR cells was 2.4-fold less than in NOS2 cells. The GST activity and mRNA level in both cell lines were constant when the cells were exposed to CDDP. Exposure to CDDP for 48 hr increased the GGT mRNA level 4.4 and 1.8 times in NOS2 and NOS2CR cells, respectively, compared with no exposure. By exposure to CDDP for 48 hr, the GGT activities in NOS2 and NOS2CR cells were increased 1.6-and 2.5-fold, respectively, compared with no exposure. The above data provide the first evidence that GGT activity and GGT mRNA are induced by CDDP in human carcinoma cell lines.

Blotting, Western↗
PubMedDate not supplied

Potentiating effect of amphotericin B on five platinum anticancer drugs in human cis-diamminedichloroplatinum (II) sensitive and resistant ovarian carcinoma cells.

We have determined an effect of amphotericin B (AMB), an antifungal drug, on the cytotoxicity of cis-diamminedichloro-platinum (II) (CDDP) and 4 CDDP analogues in a human ovarian carcinoma cell line (NOS2). Intracellular accumulation of CDDP was elevated significantly by treatment with AMB, and AMB significantly potentiated the cytotoxicity of CDDP by MTT assay. Intracellular accumulation of 4 CDDP analogues was also elevated by the treatment with AMB and the order of increasing accumulation rate of platinum drugs was consistent with that of dose modification factor (DMF). AMB also increased the intracellular CDDP accumulation in CDDP resistant cells (NOS2CR), derived from NOS2. The intracellular accumulations of 4 CDDP analogues were elevated slightly by the treatment with AMB in NOS2CR cells. DMFs of 5 platinum drugs in NOS2CR cells, however, were more than those in NOS2 cells. These results indicate that AMB sensitizes NOS2 and NOS2CR cells to platinum drugs, partially due to the increasing intracellular accumulation of these drugs. In addition, CDDP analogues are more effective in NOS2CR cells than CDDP, but the cytotoxicity of CDDP was most potentiated by AMB among the 5 platinum drugs under study.

Amphotericin B↗