Search PubMed⌕ Search

Biomedical subjects

N Kubota

Publications and source records attributed to N Kubota.

At least 73 records · Page 4Linked to original sources
PubMed1998

The phosphatidylinositol 3-kinase inhibitor wortmannin sensitizes quiescent but not proliferating MG-63 human osteosarcoma cells to radiation.

Recent genetic and biochemical studies indicate that DNA-dependent protein kinase (DNA-PK) plays an important role in DNA double-strand break (dsb) repair and V(D)J recombination. Since the catalytic subunit of DNA-PK (DNA-PKcs) has high sequence homology with phosphatidylinositol 3-kinase (PI 3-kinase), we examined the effect of wortmannin, a specific inhibitor of PI 3-kinase, on the survival of human tumor cells after X-irradiation. The present study demonstrates that wortmannin at 20 microM is an effective radiosensitizer of quiescent (Q), but not proliferating (P) cells. In addition, the rejoining of DNA dsb is significantly inhibited in Q, but not in P cells. Finally, we found that Q cell extracts have approximately five-fold less DNA-PK activity than those of P cells. After a 2 h exposure to wortmannin, the DNA-PK activity of Q cell extracts was considerably lower than that of P cells. This can explain why wortmannin sensitizes Q, but not P cells to radiation.

Androstadienes↗
PubMed1998

Matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry analysis of blue copper proteins. Azurin and mavicyanin.

Two copper proteins azurin-1 and azurin-2 were isolated from denitrifying bacteria Alcaligenes xylosoxidans GIFU1051, and the mass spectrometric analysis of the proteins were carried out by both matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI). The mass spectrometric analysis was also carried out with the recombinant zucchini protein mavicyanin, which was obtained by expression in Escherichia coli. All the proteins were detected as positive ions with the copper atom being eliminated. The molecular weights were determined as 14,017.6 for azurin-1, 13,807.6 for azurin-2 and 11,808.8 for mavicyanin. The observed molecular weight of azurin-1 agrees within two daltons with that calculated from the amino acid composition. Azurin-2 was found to have one different amino acid residue when compared with the known azurin-2 isolated from A. xylosoxidans NCIB11015. The measured molecular weight for the recombinant mavicyanin agrees within two daltons with that of calculated from the amino acid composition of the native protein; therefore, the recombinant mavicyanin is identical to the native protein.

Azurin↗
PubMed1998

Gastrinoma with multiple liver metastases: effectiveness of dacarbazine (DTIC) therapy.

Gastrinoma when associated with liver metastasis results in markedly reduced survival. However, a standard chemotherapeutic protocol for patients with unresectable tumors has not been established. We treated two patients with gastrinoma with multiple liver metastases with intravenous administration of 5-dimethyltriazenoimidazole-4-carboxamide (DTIC; dacarbazine) at a dose of 200 mg/body for 5 consecutive days. The first patient showed a marked decrease in serum gastrin levels, from 338 000 pg/ml to 22 900 pg/ml (normal range, >220pg/ml), as well as a decrease in the size and number of peripancreatic and liver tumors, after four courses of DTIC. An additional nine courses of the treatment were given, and the peripancreatic tumor was resected. The patient has been in good overall condition for more than 3(1/2) years. The second patient was treated with a total of ten courses of DTIC. Serum gastrin levels did not increase and the hepatic tumor did not change in size for more than 4 years. DTIC was effective in controlling the clinical and biochemical manifestations of gastrinoma associated with liver metastasis without serious side effects. As the toxity of DTIC is minimal, (e.g., nausea and vomiting) DTIC therapy should be considered useful for islet cell carcinomas with multiple metastases.

Aged↗
PubMed1998

Comparison between fractionated high dose rate irradiation and continuous low dose rate irradiation in spheroids.

Recent interest in clinical brachytherapy focuses on the possible radiobiological equivalence between fractionated high dose rate (HDR) and continuous low dose rate (LDR) irradiations. This study is designed to compare the radiobiological effects between the two in vitro using multicellular spheroids of human tumor. Both HDR and LDR irradiations were delivered by 137Cs source, the dose rates of which were as 1.18 Gy/min and 5.5 mGy/min, respectively. Fractionated HDR irradiation of various fraction sizes was applied twice a day. We found that: (1) The fractionated HDR irradiation (8 Gy/2 fr/day) was more effective radiobiologically than continuous LDR irradiation (8 Gy/day) and the ratio of radiobiological effects of these irradiations was estimated as 0.82, based on the 50% spheroid cure dose (SCD50); (2) the radiobiological effectiveness was independent of the fraction size of HDR irradiation administrated, and the repair of sublethal damage (SLD) was absent, suggesting that the sparing effect of fractionated HDR irradiations was absent in spheroids. Our findings could provide important information for the clinical usage of the fractionated HDR radiotherapy to replace continuous LDR radiotherapy.

Carcinoma, Squamous Cell↗
PubMed1997

SN-38, a metabolite of the camptothecin derivative CPT-11, potentiates the cytotoxic effect of radiation in human colon adenocarcinoma cells grown as spheroids.

BACKGROUND AND PURPOSE: CPT-11 (7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin) is anew semisynthesized derivative of camptothecin. SN-38 (7-ethyl-10-hydroxycamptothecin), a metabolite of CPT-11, plays a key role in the action of CPT-11. MATERIALS AND METHODS: To determine whether SN-38 potentiates the cytotoxic effect of radiation, we investigated the interaction of SN-38 and radiation in vitro in monolayer cultures and multicellular spheroids of HT-29 human colon adenocarcinoma cells. RESULTS: HT-29 spheroids were more resistant to both SN-38 and irradiation than monolayer cells. SN-38 at a concentration of 2.5 microg/ml, which by itself was not cytotoxic, greatly increased the lethal effects of radiation in spheroids, but not in monolayer cultures. Exposure to SN-38 following irradiation inhibited the potentially lethal damage repair (PLDR) in spheroids. It is suggested that the mechanism of the radiosensitization by SN-38 is due to the PLDR inhibition. CONCLUSIONS: These results indicate that CPT-11 may play a role as radiosensitizer and that a combination of CPT-11 and irradiation could prove to be a particularly effective strategy with which to treat human colon adenocarcinoma.

Adenocarcinoma↗
PubMed1997

The effect of iodine-based contrast agents on the levels of radiation-induced chromosomal aberrations.

The effects of iodine-based contrast agents on the repair of radiation-induced chromosomal damage were investigated employing peripheral blood from a healthy male donor. The blood samples were irradiated with 0.5-4.0 Gy 137Cs gamma rays. Contrast agents and NaCl solutions of various concentrations were added to the blood within the first 15 min or at 60 min after irradiation, and the samples were subsequently cultured for 45 h at 37 degrees C. Significantly elevated frequencies of chromosomal abnormalities caused by postirradiation treatment with hypertonic contrast agents appeared to increase with increasing hypertonicity. Elevated aberration frequencies were found to be greatest in the samples treated within 15 min of irradiation. The contrast agents had little effect if they were added at 60 min after irradiation, probably because the process of chromosome rejoining had been completed. Isotonic iodine-based contrast agents did not enhance the frequencies of chromosomal aberrations to a significant degree.

Adult↗
PubMed1997

[Acute myeloid leukemia with monosomy 7 accompanied by central diabetes insipidus].

A 27-year-old female was diagnosed as having atypical aplastic anemia in 1979 because of hypercellular bone marrow with abnormal erythroblasts and megakaryocytes. Afterward the diagnosis was corrected to myelodysplastic syndrome (RA) due to the reevaluation of the bone marrow smears. In March, 1995, thirst and polyurea occurred. In April, 1995, bone marrow aspiration biopsy showed the proliferation of atypical blasts (28%), and two months later, the number of the blasts increased (30%) and leukemic progression was noticed. Only 0.5 percent of the blasts showed weak peroxidase activity, and most of the blasts had CD13, CD33 and several adhesion molecules as CD11a, CD11b, CD44, CD54 and CD56. Karyotype of the bone marrow cells was 45, XX, -7. Her polyurea was caused by central diabetes insipidus. She was also complicated by pleuritis, colon ulcer, sinusitis and hypothalamic dysfunction. The etiology of these signs was due to the leukemic cell infiltration. She died despite of receiving multi-drug chemotherapy.

Adult↗
PubMed1997

[Four cases of late infection following scleral buckling procedure].

We report four cases with late infection following a scleral buckling procedure. These cases were a 44-year-old male, a 52-year-old female, a 59-year-old male, and a 60-year-old male. All of these cases developed conjunctival injection, chemosis, and mucopurulent discharge 7 to 15 years after the procedure. The symptoms did not improve despite months of medical therapy, suggesting scleral buckle infection, and finally the buckling materials were removed. Solid silicone was used in 2 cases, and a sponge was used in 2 cases, with encircling elements in 1 case, and without encircling elements in 3 cases. Pus culture of the removal exoplant revealed fungaul infection in 2 cases. The others were negative, but bacterial infection was suspected from their clinical course and intraoperative findings. After removal of the buckles, the symptoms improved rapidly in all cases and there was no recurrence of retinal detachment. Scleral buckle infection should be suspected and removal of buckling materials should be considered, in cases with refractory conjunctival and scleral inflammation even years after scleral buckling procedure.

Adult↗
PubMed1997

Induction of a particular deletion in mitochondrial DNA by X rays depends on the inherent radiosensitivity of the cells.

We examined whether X radiation induces a particular deletion in the mitochondrial DNA (mtDNA) of the cells of two human squamous cell carcinoma lines with different sensitivity to radiation and in a radiosensitive ataxia telangiectasia (AT) cell line. We used polymerase chain reaction (PCR) to quantify the accumulation of a particular 4977-bp deletion (delta mtDNA4977). PCR products of delta mtDNA4977 were detectable after exposure to 10 Gy in the radioresistant squamous cell carcinoma cells, 2 Gy in the radiosensitive squamous cell carcinoma cells and 1 Gy in the radiosensitive AT cells. These observations suggest that ionizing radiation induces the delta mtDNA4977 in human cells and that the radiation doses required to induce this deletion reflect the sensitivity of cells to radiation.

Carcinoma, Squamous Cell↗
PubMed1996

ACE-inhibitor-induced cough, an adverse drug reaction unrecognised for several years: studies in prescription-event monitoring.

OBJECTIVE. This study examines cough recorded in Prescription-Event Monitoring (PEM) of four ACE-inhibitors. Particular attention was paid to the study of enalapril because the drug was monitored before the causal relationship between cough and ACE-inhibitors had been widely accepted. RESULTS. Several factors which had obscured the causal relationship in the individual cases were found to be also an obstacle in PEM. For example, cough was a common and non-serious event and was under-reported in the PEM study of enalapril and the rate was not strikingly different from that recorded for other drugs. Cough induced by ACE-inhibitors has several characteristics which reduce the chance of a recognisable "signal'. The original questionnaires returned from doctors in the PEM study of enalapril have been reexamined. The observation that the rate of cough diminished after enalapril had been stopped rather than increased after starting, provided the best evidence of causality, because this was not affected by many biases such as the publicity that had occurred prior to doctors participating in PEM completed later reports.

Adult↗
PubMed1996

Clinical significance of LEA-1 expression in adult acute myeloid leukemia.

In this study, we examined expressions of several adhesion molecules (AdMs), i.e. leukocyte function antigen-1 (LFA-1: CD11a/CD18), Hermes homing receptor (CD44) and intercellular adhesion molecule-1 (ICAM-1: CD54), on leukemia cells from 51 adult patients with newly diagnosed acute myeloid leukemias (AMLs) to elucidate clinical significance of these AdM expressions. Those expressions in lymphoid malignancies have been correlated with tumor evolutions, but CD44 was detected in all the AML cases examined and CD54 expression did not associate with their clinical characteristics or outcomes. However, we found that LFA-1 expressions significantly correlated with splenomegaly, resistance to induction chemotherapies and short survival periods in AML patients.

Acute Disease↗
PubMed1996

Phosphorylated sites of M(r) 25,000 protein, a putative protein phosphatase 2A modulator, and phosphorylation of the synthetic peptide containing these sites by protein kinase C.

The M(r) 25,000 protein isolated from Xenopus laevis oocytes was shown to be an effective phosphate acceptor for Ca(2+)-phospholipid-dependent protein kinase (protein kinase C) [Hashimoto, E. et al. (1995) J. Biochem. 118, 453-460]. In this study, the sites of this protein phosphorylated by protein kinase C were determined and the mechanism of substrate recognition was studied using a synthetic peptide containing the phosphorylation sites. After incorporation of about 2 mol of phosphate per mol of this protein, the radioactive protein was digested with trypsin and the phosphopeptides were purified by a series of column chromatographies. The amino acid sequence of the major radioactive peptide was shown to be Ser-Arg-Val-Ser-Lys-Arg. This and previous results suggest that the two serine residues at the amino-terminal region were phosphorylated by protein kinase C. To confirm this, the phosphorylated protein was directly analyzed for the amino acid sequence. The percent distribution of dithiothreitol adduct of the phenylthiohydantoin derivative of serine (PTH-serine) compared with that of PTH-serine increased at the first and fourth cycles of the sequence analysis. When the synthetic peptide composed of the amino-terminal eleven amino acids was employed as phosphate acceptor, the Km value was unexpectedly high (1.1 mM) compared with that of the native protein (0.5 muM). A stimulatory effect of M(r) 25,000 protein on the activity of protein phosphatase 2A was further enhanced after phosphorylation by protein kinase C. These results suggest that the two serine residues recognized by protein kinase C may have some role in the regulation of this M(r) 25,000 protein.

Amino Acid Sequence↗
PubMed1996

Results of surgery for paralytic exotropia due to oculomotor palsy.

In 138 cases of paralytic exotropia due to oculomotor palsy, transposition of the superior oblique muscle and resection of the medial rectus muscle were carried out. Surgery was performed with or without recession of the lateral rectus muscle. The long-term prognosis for 4 years or more was observed in 35 cases. We found that the same results could be obtained by selecting transposition of the superior oblique muscle in cases of complete palsy and resection of the medical rectus muscle in cases of incomplete palsy. There was no benefit in combining resection of the medial rectus muscle when performing the transposition of the superior oblique muscle. Regardless of which method was used, a combination with recession of the lateral rectus muscle greatly improved the effectiveness of the procedure.

Adolescent↗
PubMed1996

The 69-84 amino acid region of the parathyroid hormone molecule is essential for the interaction of the hormone with the binding sites with carboxyl-terminal specificity.

We evaluated the competitive inhibitory effect of intact PTH, the amino-terminal PTH(1-34) fragment, and a series of truncated carboxyl-terminal PTH fragments on the binding of internally 35S-labeled human PTH(1-84) ([35S]hPTH(1-84)) to osteoblastic cells (ROS 17/2.8), in order to identify the minimum and critical elements within the PTH molecule for the interaction with the binding sites specific for the carboxyl-terminal region of the hormone. When the amino-terminal region of the PTH molecule was truncated stepwise, hPTH(35-84), hPTH(53-84) and hPTH(69-84), but not hPTH(70-84), significantly inhibited the [35S]hPTH(1-84) binding. On the other hand, the simple deletion of the carboxyl-terminal glutamine at position 84 of hPTH(53-84) [hPTH(53-83)] resulted in blunting the inhibitory effect of the peptide on the [35S]hPTH(1-84) binding. Furthermore, hPTH(35-84), hPTH(53-84) and hPTH(69-84), but not hPTH(70-84) nor hPTH(53-83), augmented the inhibitory effect of the amino-terminal PTH fragment [hPTH(1-34)] on the [35S]hPTH(1-84) binding. Of special interest was that the combination of hPTH(1-34) and hPTH(35-84) reproduced the inhibitory effect of unlabeled hPTH(1-84) on the [35S]hPTH(1-84) binding, on an equimolar basis. The 69-84 region of the PTH molecule thus appears to be crucial for binding to the carboxyl-terminal specific binding sites for PTH in osteoblasts. The interaction of the amino-terminal and carboxyl-terminal regions of a PTH molecule with their own respective binding sites seemed to occur in a fairly independent manner.

Alkaline Phosphatase↗
PubMed1996

[Structure and magnetic resonance imaging of the fiber connection between Whitnall's ligament and the superior wall of the orbit].

To confirm the structure of the fiber connection between Whitnall's ligament and the superior wall of the orbit, we observed ten orbits of five Japanese cadavers by magnetic resonance imaging (MRI) and dissection. Our findings were as follows: MRI showed a well-circumscribed low-intensity signal at the fiber connection. Preaponeurotic fat was prominent, and the fibers originating from Whitnall's ligament were fused at the lower face of the capsule of the preaponeurotic fat in four cadavers. The fibers originating from the upper face of the fat were attached to the superior periorbit (minimum width, 15 mm). The fifth cadaver had little preaponeurotic fat and few fibers. These anatomic differences may be within the normal range of variation. We believe that the fibers support Whitnall's ligament and help to retract preaponeurotic fat during levator muscle contraction as the eye opens.

Adipose Tissue↗