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Biomedical subjects

K Niikura

Publications and source records attributed to K Niikura.

At least 19 recordsLinked to original sources
PubMed2006

mu-Opioid receptor internalization-dependent and -independent mechanisms of the development of tolerance to mu-opioid receptor agonists: Comparison between etorphine and morphine.

A growing body of evidences suggests that receptor desensitization is implicated in the development of tolerance to opioids, which is generally regulated by protein kinases and receptor trafficking proteins. In the present study, we demonstrated that repeated s.c. treatment with etorphine, but not morphine, produced a significant increase in protein levels of G protein-coupled receptor kinase 2, dynamin II, beta-arrestin 2 and phosphorylated-conventional protein kinase C in membranes of the mouse spinal cord, suggesting that the etorphine-induced mu-opioid receptor desensitization may result from G protein-coupled receptor kinase 2/dynaminII/beta-arrestin2-dependent phosphorylation of mu-opioid receptors. Unlike etorphine, morphine failed to change the levels of these trafficking proteins. Furthermore, we found that the level of glial fibrillary acidic protein in the mouse spinal cord was clearly increased by chronic in vivo and in vitro treatment with morphine, whereas no such effect was noted by etorphine. In the behavioral study, intraperitoneal pretreatment with the glial-modulating agent propentofylline suppressed the development of tolerance to morphine-induced antinociception. In addition, intrathecal injection of astrocytes and astrocyte-conditioned medium mixture, which were obtained from cultured astrocytes of the newborn mouse spinal cord, aggravated the development of tolerance to morphine. In contrast, these agents failed to affect the development of tolerance induced by etorphine. These findings provide direct evidence for the distinct mechanisms between etorphine and morphine on the development of tolerance to spinal antinociception. These findings raise the possibility that the increased astroglia response produced by chronic morphine could be associated with the lack of mu-opioid receptor internalization.

Animals↗
PubMed2006

Comparative analysis of the effects of a novel vacuolar adenosine 5'-triphosphatase inhibitor, FR202126, and doxycycline on bone loss caused by experimental periodontitis in rats.

BACKGROUND: Doxycycline is reported to inhibit alveolar bone destruction by blocking matrix metalloproteinases (MMPs). Nevertheless, MMPs are not involved in osteoclastic bone resorption; osteoclasts directly resorb bone. An acidic microenvironment, which is formed by vacuolar adenosine 5'-triphosphatase (V-ATPase) expressed in the plasma membranes of osteoclasts, is indispensable for osteoclastic bone resorption. In the present study, we investigated the potential role of the acidic environment on periodontal bone destruction using a novel and specific V-ATPase inhibitor, FR202126, which we compared to doxycycline. METHODS: Inhibitory activity against in vitro bone resorption was examined by measuring the Ca2+ release from murine calvariae cultured for 6 days, which were treated with interleukin-1 (IL-1), IL-6, or parathyroid hormone. Experimental periodontitis was induced by a ligature wire tied around the contact between the first and second maxillary molars of male Wistar rats. FR202126 and doxycycline were administered orally once daily for 6 days. Seven days after tying, the maxillae were dissected and mesiodistal longitudinal paraffin sections, including interdental alveolar bone, were processed for histopathologic analysis. RESULTS: FR202126 inhibited bone resorption almost completely in calvaria cultures induced by three stimulators, whereas doxycycline was unable to prevent in vitro bone resorption. Oral administration of FR202126 significantly prevented alveolar bone loss in experimental periodontitis. However, doxycycline did not inhibit alveolar bone destruction. CONCLUSION: These results suggest that an acidic microenvironment plays a more important role than MMPs in periodontal alveolar bone destruction and that V-ATPase inhibitors may offer a new approach to the treatment of periodontal disease.

Alveolar Bone Loss↗
PubMed2001

Direct monitoring kinetic studies of DNA polymerase reactions on a DNA-immobilized quartz-crystal microbalance.

Catalytic reactions of DNA polymerase I from E. coli (Klenow fragment, KF) were monitored directly with a template/primer (40/25- or 75/25-mer)-immobilized 27-MHz quartz-crystal microbalance (QCM). The 27-MHz QCM is a very sensitive mass-measuring device in aqueous solution, as the frequency decreases linearly with increasing mass on the QCM electrode at the nanogram level. Three steps in polymerase reactions which include 1) binding of DNA polymerase to the primer on the QCM (mass increase); 2) elongation of complementary nucleotides along the template (mass increase); and 3) release of the enzyme from the completely polymerized DNA (mass decrease), could be monitored continuously from the time dependencies of QCM frequency changes. The binding constant (Ka) of KF to the template/primer DNA was 10(8)M(-1) (k(on) = 10(5)M(-1)s(-1) and k(off)= 10(-3)s(-1)), and decreased to 10(6)M(-1) (k'on = 10(4)M(-1)s(-1) and k'off = 10(-2)s(-1)) for completely polymerized DNA. This is due to the 10-fold decrease in binding rate constant (k(on)) and 10-fold increase in dissociation rate constant (k(off)) for completed DNA strands. Ka values depended slightly on the template and primer sequences. The kinetic parameters in the elongation process (k(cat) and Km) depended only slightly on the DNA sequences. The repair process during the elongation catalyzed by KF could also be monitored in real time as QCM frequency changes.

Base Pair Mismatch↗
PubMed2001

Design and characterization of asparagine- and lysine-containing alanine-based helical peptides that bind selectively to A.T base pairs of oligonucleotides immobilized on a 27 mhz quartz crystal microbalance.

We have systematically designed and synthesized six kinds of 16-17 mer alanine-based peptides containing four to six lysine (K) and one to four asparagine (N) residues to achieve the selective binding to A.T base pairs of DNA duplexes. The position and number of K and N residues were changed in the helical structure according to common features of the DNA-binding proteins, in which K and N residues are expected to interact electrostatically with phosphate groups and to interact with A.T base pairs by hydrogen bonding, respectively. The time courses of binding of these peptides to dA(30).dT(30) and dG(30).dC(30) duplexes immobilized on a 27 MHz quartz crystal microbalance (QCM) were studied in 10 mM phosphate buffer (pH 7.5) and 40 mM NaCl at 10 degrees C. The maximum binding amounts (Deltam(max)) on a nanogram scale and binding constants (K(a)) could be obtained from the frequency decrease (mass increase) of the oligonucleotide-immobilized QCM. The conformation changes of the peptides upon binding to DNAs were monitored by circular dichroism (CD) spectroscopy. The four properly arranged N residues in the six-cationic K peptide, K6N4(d), resulted in a 5-fold higher affinity for A.T base pairs (K(a) = 5.9 x 10(5) M(-1)) than for G.C base pairs (K(a) = 1.2 x 10(5) M(-1)), and alpha-helices were clearly promoted by the binding to A.T base pairs from CD spectral changes.

Adenine↗
PubMed2000

[Two cases of idiopathic membranous nephropathy with focal and segmental glomerulosclerotic lesions in which renal function progressively deteriorated].

Previous reports have clarified that focal and segmental glomerulosclerosis(FSGS) appearing in membranous nephropathy(MN) is associated with a poorer prognosis than that of MN without FSGS. However, the etiology and pathogenesis of such FSGS lesions may show substantial individual differences. In some patients, hemodynamic alterations secondary to hypertension and vascular disorders seem to play a crucial role in the development of such FSGS lesions. In such instances, steady regulation of blood pressure might slow down further progression of FSGS lesions. Here we describe two cases of biopsy-proven MN with FSGS. Case I was a 44-year-old man who had shown massive proteinuria with hematuria at the age of 39 years. Renal biopsy specimens obtained at the age of 40 and 41 years showed MN without FSGS and MN with FSGS, respectively. His blood pressure control was fairly good throughout the course. Although he was on a steroid, an immunosuppressant, a low protein diet, and an ACE inhibitor, his renal function declined in 5 years. Case 2 was a 61-year-old woman who showed nephrotic syndrome at the age of 39 years. A renal biopsy specimen obtained at the age of 58 years showed MN with FSGS and remarkable atherosclerotic changes of the interlobular arteries. Her blood pressure control was rather poor throughout the course. Her renal function gradually declined over 22 years. Since parts of the FSGS lesions of the second case may have been caused by hypertension, it is tempting to speculate that day-to-day control of blood pressure could improve the long-term prognosis. We believe that, at least in some patients of MN with FSGS, careful management may lead to a more favorable course of decline in renal function.

Adult↗
PubMed1999

Effect of plasma exchange on refractory hemophagocytic syndrome complicated with myelodysplastic syndrome.

A case of hemophagocytic syndrome (HPS) refractory to corticosteroid therapy was successfully treated by plasma exchange. The patient was a 56-year-old woman who had undergone regular hemodialysis for 10 years for complicated myelodysplastic syndrome (MDS) and then had had lung tuberculosis. After the onset of tuberculosis, she suffered from HPS and was treated by antituberculosis agents and high dose corticosteroid administration without any effect on the HPS. After adding a series of plasma exchanges, the HPS improved gradually, and her MDS began to respond to corticosteroid therapy. Plasma hypercytokinemia due to HPS was corrected by plasma exchange, and the correction of a high level of plasma inflammatory cytokine was considered to be one of the contributing factors for the improvement of HPS. These results suggest that therapeutic plasma exchange should be considered as a therapeutic tool for HPS refractory to conventional therapy.

Adolescent↗
PubMed1999

WF14861, a new cathepsins B and L inhibitor produced by Colletotrichum sp. II. Biological properties.

WF14861, 3-(N-(1-(N-(4-aminobutyl)-N-(3-aminopropyl)carbamoyl)-2-(4-hydroxyphenyl )ethyl)carbamoyl)oxirane-2-carboxylic acid, was obtained from the culture mycelium of Colletotrichum sp. as a novel cathepsins B and L inhibitor. WF14861 also showed inhibitory activities against bone derived crude protease and other cysteine proteases in vitro. The compound ameliorated the tissue damage and the bone destruction models of low-calcium-diet-fed mouse and adjuvant arthritis rat model.

Animals↗
PubMed1998

Kinetic studies of sequence-specific binding of GCN4-bZIP peptides to DNA strands immobilized on a 27-MHz quartz-crystal microbalance.

Specific protein-DNA interaction was studied quantitatively by using a highly sensitive 27-MHz quartz-crystal microbalance (QCM). Biotinylated DNA double strands (21 bp, having a CRE site of 5'ATGACGTCAT3') were immobilized on an avidin-bound QCM surface, and sequence-specific binding of bZIP 56-mer peptides (having both the basic region for binding and the leucine zipper region for dimerization) to the DNA strand on the QCM was observed. The binding amount (Deltam) at the nanogram level and kinetic parameters such as association constants (Ka) and binding and dissociation rate constants (k1 and k-1) could be obtained from time courses of QCM frequency decreases. A bZIP peptide as a dimer was observed to bind sequence-specifically to one DNA strand having a CRE site. Ka values of ss-bZIP, in which the leucine-zipper region of bZIP was substituted by a Cys-Cys linkage, were largely decreased, and the sequence selectivity also disappeared. Ka values obtained by the QCM method showed good agreement with those obtained from the conventional gel mobility shift assay or from circular dichroism spectrum changes. When the specific sequence of the CRE site of DNA strands was partly changed, Ka values decreased by about a half due to the increase of the dissociation rate constant (k-1) independent of the binding rate constant (k1).

Amino Acid Sequence↗
PubMed1998

Kinetic measurements of DNA hybridization on an oligonucleotide-immobilized 27-MHz quartz crystal microbalance.

A highly sensitive 27-MHz quartz-crystal microbalance, on which a 10-30-mer oligonucleotide was immobilized as a probe molecule, was employed to detect hybridization of complementary oligonucleotides in aqueous solution. From frequency decreases (mass increases due to the hybridization) with passage of time, kinetic parameters such as association constants (K(a)) and binding and dissociation rate constants (k(1) and k(-1)) could be obtained, as well as binding (hybridization) amount at the nanogram level (delta m). Kinetic studies were carried out by changing various parameters: (i) the immobilization method of a probe oligonucleotide on Au electrode, (ii) number of mismatching bases in sequences of target oligonucleotides, (iii) length of both probe and target oligonucleotides, (iv) hybridization temperature, and (v) ionic strength in solution. The obtained results were compared with those obtained by a surface plasmon resonance method using a BIAcore system.

Avidin↗
PubMed1996

rHuEPO enhances the production of plasminogen activator inhibitor-1 in cultured endothelial cells.

The direct effects of recombinant human erythropoietin(rHuEPO) on coagulation and fibrinolysis factors were evaluated in a cultured endothelial cell (EC) system. Confluent quiescent ECs were incubated with or without 5.0 U/ml rHuEPO for 1, 6, and 18 hours, and supernatant concentrations of plasminogen activator inhibitor-1 (PAI-1): antigen (Ag), tissue plasminogen activator and thrombomodulin, and supernatant activities of tissue factor pathway inhibitor and von Willebrand factor were measured. The results showed that only PAI-1 levels were increased by the presence of rHuEPO. In order to assess the effect of rHuEPO on PAI-1 production by EC more precisely, confluent ECs were incubated with various doses of rHuEPO (0, 1.0, 2.5, 5.0, 10.0 U/ml) for 1, 6, 12, and 18 hours, and PAI-1:Ag concentrations in the supernatants of media were measured. PAI-1:Ag in the supernatants were increased by the presence of rHuEPO at all incubation times (P < 0.01) and the increase in PAI-1:Ag was dependent on rHuEPO concentration. The increases in PAI-1:Ag by 5.0 U/ml rHuEPO were comparable to those by 0.1 U/ml tumor necrosis factor-alpha, 1.0 microgram/ml lipopolysaccharide, and 0.5 U/ml thrombin. The increase in PAI-1:Ag by rHuEPO was suppressed by pre-incubation with 10 micrograms/ml cycloheximide (P < 0.01) or 0.2 microgram/ml actinomycin D (P < 0.01). These results indicate that rHuEPO directly stimulates PAI-1 production in cultured EC via de novo protein and RNA syntheses.

Cells, Cultured↗
PubMed1995

Relative hypoparathyroidism in hemodialysis patients.

To clarify the incidence and contributing factors of hypoparathyroidism in a hemodialysis (HD) population, 224 patients undergoing maintenance HD were investigated. They were divided into 4 groups according to their high-sensitive parathyroid hormone levels: extra-high (EH) group > 420,000 pg/ml; high (H) group 20,000-420,000 pg/ml; moderate (M) group 4,500-20,000 pg/ml; low (L) group, < 4,500 pg/ml. In group L, a 25-mg/kg deferoxamine (DFO) infusion test was undertaken to estimate aluminum (Al) accumulation. The distribution in each group was 42, 35, 12, and 11% for groups L, M, H and EH, respectively. Group-L patients were relatively older than those of the other groups. Diabetes was seen in 20% of group-L patients, as opposed to no diabetes in groups H and EH. Among the 22 diabetics, 82% were in group L. 70% of group-L patients showed a less than 50-micrograms/l Al increment after the DFO infusion test. Bone mineral density (BMD) did not differ between the groups with relative hypoparathyroidism (RHP=L) and background-matched non-RHP, either at the initiation of HD or the recent period, and the changes in BMD were comparable between the 2 groups. These results suggest that a considerable number of HD patients show RHP. Diabetes, but not Al accumulation, was considered to be one of the predisposing factors of RHP. Though the outcome of RHP will be aplastic bone disease (ABD) in HD patients, the clinical significance of ABD has not been fully evaluated. Further studies are required to clarify the precise mechanisms of RHP and the significance of ABD.

Adult↗
PubMed1991

[The effects and pharmacokinetics of rhG-CSF on the treatment of neutropenia in patients with renal failure].

rhG-CSF (recombinant human granulocyte colony stimulating factor) promotes production and release of neutrophil from bone marrow, and it enhances neutrophil function. In this study, the pharmacokinetics, effects on neutrophil and immune functions and efficacy and safety of rhG-CSF were studied in patients with end-stage renal failure (CRF). To 9 patients with CRF; 2 patients on conservative therapy and 7 patients under regular hemodialysis, 50 micrograms/m2 rhG-CSF were administered intravenously under the schedule of single or 2 week consecutive injection. In single injection study, serial changes in plasma rhG-CSF concentration and peripheral blood cell count were examined following the administration. In consecutive injection study, plasma rhG-CSF concentration, anti-rhG-CSF antibody, peripheral blood cell counts, blood chemistry and coagulation factors, and neutrophil and immune functions were examined. As the results, 1) Half life of rhG-CSF, 2.87 +/- 0.65 hr, was about 2 times longer than that in healthy subjects, and it was not affected by hemodialysis treatment. 2) Marked increase in leukocyte and neutrophil counts and mild increase in lymphocyte count were observed during single and consecutive administration of rhG-CSF. There was no significant change in other leukocyte differentiations, RBC, or platelet count. 3) Neutrophil alkaline phosphatase score increased significantly during single and consecutive administration, and other neutrophil function also improved in several patients with impaired neutrophil function. 4) Slight bone pain and increase in serum alkaline phosphatase were observed in about a half of patients during consecutive injection study. Neither antibody nor accumulation of rhG-CSF was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[The effects of r-HuEPO on platelet function and coagulation factors in hemodialysis patients].

To evaluate the effects of correction of anemia with recombinant human erythropoietin (r-HuEPO) on the hemostatic defects in uremia, hemostatic parameters were examined in 18 patients with renal anemia receiving hemodialysis (HD). During the study, hematocrit (Ht) increased from 22.9 +/- 3.1% (mean +/- SD) at pre-treatment (stage-I) to 31.0 +/- 3.0% 12 weeks after 3000 IU intravenous r-HuEPO administration at the end of every HD (stage-II), and decreased to 26.2 +/- 4.2% 6 weeks after r-HuEPO discontinuation (stage III). Platelet count did not change among these three stages, however, mean platelet volume significantly increased at stage II compared to stage I. Ivy bleeding time (Ivy-BT) significantly shortened at stage II (I; 14.3 +/- 6.0, II; 10.1 +/- 6.5 min, p less than 0.01), and prolonged again at stage III (p less than 0.05 vs stage II). Among the patients, 6 out of 18 patients did not show any reduction in Ivy-BT (unchanged group). Though there were no significant changes in platelet aggregation rates, plasma TxB2, 6-keto-PGF1 alpha, F. VIII: C, and F. VIII: Ag levels throughout the study, platelet adhesion rate was significantly improved at stage II (I; 11.8 +/- 6.8, II; 19.6 +/- 12.8%, p less than 0.05), and similar augmentation in vWf: Ag was observed. Improvement in these two parameters were more remarkable in shortened Ivy-BT group (n = 12) than in unchanged group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Plastic operation of alveolar process by visor osteotomy].

Extraction of teeth from the lower jaw often results in atrophy of the alveolar process and mandibular body, and sometimes the atrophy progresses so severely as to seriously affect the fitness of the denture, especially the full denture. If the alveolar ridge is markedly resorbed, patients are not satisfied, unless the alveolar process is surgically heightened and the fitness of the denture is regained. Plastic operation of the alveolar process by visor osteotomy and grafting of the iliac bone was performed on a 54-year-old woman who presented at our Department with a complaint of unfitness of the full denture because of marked atrophy of the mandibular alveolar process. As a result of this operation, a functionally well-fitting denture could be fitted to the satisfaction of this patient. This paper describes the outline of the surgical procedure.

Alveolar Ridge Augmentation↗