Search PubMed⌕ Search

Biomedical subjects

K Nitta

Publications and source records attributed to K Nitta.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structure of the YSPTSPS repeat containing two SPXX motifs in the CTD of RNA polymerase II: NMR studies of cyclic model peptides reveal that the SPTS turn is more stable than SPSY in water.

The carboxyl-terminal domain of RNA polymerase II, which is rich in phosphorylation sites, contains 17--52 tandem repeats with the consensus sequence of the heptapeptide, YSPTSPS. The repeat unit of the heptapeptide has two SPXX motifs showing potential beta-turns, SPTS and SPSY. NMR studies were performed in water at pH 4.0 for two cyclic peptides containing one and two repeat units, cyclo-[C(1)R(2)D(3)Y(4)S(5)P(6)T(7)S(8)P(9)S(10)Y(11)S(12)R(13)D(14)C(15)] (peptide 1) and cyclo-[C(1)R(2)D(3)Y(4)S(5)P(6)T(7)S(8)P(9)S(10)Y(11)S(12)P(13)T(14)S(15)P(16)N(17)Y(18)S(19)R(20)D(21)C(22)] (peptide 2), which are cyclized with a disulfide bridge of two Cys residues at the N- and C-termini. SP in 1 and 2 are predominantly in trans form. The following NMR parameters were detected: (1) lower temperature coefficients of amide proton chemical shifts of T7 and S8 in 1, and Tx (T7 or T14), Sx (S8 or S15), Tz (T14 or T7) and Sz (S15 or S8) in 2, (2) significantly large deviation of H(alpha) chemical shifts from its random coil value (Delta H(alpha)) of Pro preceding the Thr (P6 in 1, and Px and Pz in 2), (3) relatively large (3)J(HNH alpha) coupling constants (>8.7 Hz) of T7 in 1 and Tx and Tz in 2, and (4) NOE (d(NN) (i, i+1)) connectivities between the amide protons of T7-S8 and S10-Y11 in 1, and Tx-Sx, S10-Y11, Tz-Sz, and N17-Y18 in 2, although two Pro-Thr-Ser segments in 2 (each of these are annotated by 'x' and 'z') in the first and second repeat units were not distinguishable. Comparison of the NMR parameters between the cyclic peptides and the corresponding linear peptides indicates that cyclization promotes structural stabilization in water. The present NMR data were consistent with the presence of a beta-turn at both SPTS and SPSY: S(5)P(6)T(7)S(8) and S(8)P(9)S(10)Y(11) in 1, and SPxTxSx, SPzTzSz, SP(9)S(10)Y(11), SP(16)N(17)Y(18) in 2. However, the structure of the SPTS segment is more stable than that of the SPSY segment. Conformations consistent with NMR parameters including NOE distances were obtained through molecular dynamics and energy minimization methods. These calculations yielded two stable conformers for the SPTS segment. One of the two corresponds to a type I beta-turn.

Amino Acid Sequence↗
PubMed2001

Structure and activity of the insect cytokine growth-blocking peptide. Essential regions for mitogenic and hemocyte-stimulating activities are separate.

Growth-blocking peptide (GBP) is a 25-amino acid insect cytokine found in Lepidopteran insects that possesses diverse biological activities such as larval growth regulation, cell proliferation, and stimulation of immune cells (plasmatocytes). The tertiary structure of GBP consists of a structured core that contains a disulfide bridge and a short antiparallel beta-sheet (Tyr(11)-Arg(13) and Cys(19)-Pro(21)) and flexible N and C termini (Glu(1)-Gly(6) and Phe(23)-Gln(25)). In this study, deletion and point mutation analogs of GBP were synthesized to investigate the relationship between the structure of GBP and its mitogenic and plasmatocyte spreading activity. The results indicated that deletion of the N-terminal residue, Glu(1), eliminated all plasmatocyte spreading activity but did not reduce mitogenic activity. In contrast, deletion of Phe(23) along with the remainder of the C terminus destroyed all mitogenic activity but only slightly reduced plasmatocyte spreading activity. Therefore, the minimal structure of GBP containing mitogenic activity is 2-23 GBP, whereas that with plasmatocyte spreading activity is 1-22 GBP. NMR analysis indicated that these N- and C-terminal deletion mutants retained a similar core structure to wild-type GBP. Replacement of Asp(16) with either a Glu, Leu, or Asn residue similarly did not alter the core structure of GBP. However, these mutants had no mitogenic activity, although they retained about 50% of their plasmatocyte spreading activity. We conclude that specific residues in the unstructured and structured domains of GBP differentially affect the biological activities of GBP, which suggests the possibility that multifunctional properties of this peptide may be mediated by different forms of a GBP receptor.

Amino Acid Sequence↗
PubMed2001

Solar 8B and hep neutrino measurements from 1258 days of Super-Kamiokande data.

Solar neutrino measurements from 1258 days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0-20.0 MeV. The measured solar neutrino flux is 2.32+/-0.03(stat)+0.08-0.07(syst)x10(6) cm(-2) x s(-1), which is 45.1+/-0.5(stat)+1.6-1.4(syst)% of that predicted by the BP2000 SSM. The day vs night flux asymmetry (Phi(n)-Phi(d))/Phi(average) is 0.033+/-0.022(stat)+0.013-0.012(syst). The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a 90% C.L. upper limit of 40x10(3) cm(-2) x s(-1), which is 4.3 times the BP2000 SSM prediction.

Journal Article↗
PubMed2001

Constraints on neutrino oscillations using 1258 days of Super-Kamiokande solar neutrino data.

We report the result of a search for neutrino oscillations using precise measurements of the recoil electron energy spectrum and zenith angle variations of the solar neutrino flux from 1258 days of neutrino-electron scattering data in Super-Kamiokande. The absence of significant zenith angle variation and spectrum distortion places strong constraints on neutrino mixing and mass difference in a flux-independent way. Using the Super-Kamiokande flux measurement in addition, two allowed regions at large mixing are found.

Journal Article↗
PubMed2001

Fourier-transform infrared spectroscopic study of Ca2+-binding to osteocalcin.

Osteocalcin, the gamma-carboxyglutamic acid-containing protein, which is the most abundant noncollagenous protein of bone and dentin, is considered to play roles in bone formation and remodeling. It is unclear how the gamma-carboxyglutamic acid side-chains in osteocalcin coordinate to Ca2+, since the X-ray structure of osteocalcin is not available. Interactions between Ca2+ and the gamma-carboxyglutamic acid side-chains in osteocalcin were investigated by Fourier-transform infrared spectroscopy. In the region of the antisymmetric stretches, the loss of intensity at 1574 cm(-1) and gain of intensity at 1600 cm(-1) were observed due to Ca2+-binding to osteocalcin. The spectral changes indicate that the gamma-carboxyglutamic acid side-chains in osteocalcin coordinate to Ca- in the malonate chelation mode, where a Ca2+ interacts with two oxygen atoms, one from each of the two COO- groups of a single gamma-carboxyglutamic acid residue. Addition of Ca2+ does not cause any spectral change in the spectra of decarboxylated osteocalcin since the gamma-carboxyglutamic acid residues are converted to the glutamic acid residues by chemical modification.

Animals↗
PubMed2001

Leczyme.

Explore the source record for details and available documents.

Amphibian Proteins↗
PubMed2001

The CEEF, closed ecosystem as a laboratory for determining the dynamics of radioactive isotopes.

Nuclear power generation is now confronted with a very difficult situation all over the world because of the problems of radioactive waste disposal and of the accidents, which have occurred. Nuclear power generation now supplies nearly 30% of total electric power demand in Japan. Therefore it is very difficult to change quickly the construction plans of nuclear facilities already designed. A nuclear fuel reprocessing center is now under construction in Rokkasho-Mura in Aomori Prefecture. If this center starts its operation, small amounts of 14CO2 are expected to be released into the atmosphere and will enter the global cycle. The simulation experiment of 14C trace amounts which enter into ecosystems is now being planned using stable isotope 13C within CEEF (Closed Ecology Experiment Facilities).

Air Pollution, Radioactive↗
PubMed2001

Application of crop gas exchange and transpiration data obtained with CEEF to global change problem.

In order to predict carbon sequestration of vegetation with the future rise in atmospheric CO2 concentration, [CO2] and temperature, long term effects of high [CO2] and high temperature on responses of both photosynthesis and transpiration of plants as a whole community to environmental parameters need to be elucidated. Especially in the last decade, many studies on photosynthetic acclimation to elevated [CO2] at gene, cell, tissue or leaf level for only vegetative growth phase (i.e. before formation of reproductive organs) have been conducted all over the world. However, CO2 acclimation studies at population or community level for a whole growing season are thus far very rare. Data obtained from repeatable experiments at population or community level for a whole growing season are necessary for modeling carbon sequestration of a plant community. On the other hand, in order to stabilize material circulation in the artificial ecological system of Closed Ecology Experiment Facilities (CEEF), it is necessary to predict material exchange rates in the biological systems. In particular, the material exchange rate in higher plant systems is highly variable during growth periods and there is a strong dependence on environmental conditions. For this reason, dependencies of both CO2 exchange rate and transpiration rate of three rice populations grown from seed under differing conditions of [CO2] and day/night air temperature (350 microL CO2 L-1, 24/17 degrees C (population A); 700 microL CO2 L-1, 24/17 degrees C (population B) and 700 microL CO2 L-1, 26/19 degrees C (population C)) upon PPFD, leaf temperature and [CO2] were investigated every two weeks during whole growing season. Growth of leaf lamina, leaf sheath, panicle and root was also compared. From this experiment, it was elucidated that acclimation of instantaneous photosynthetic response of rice population to [CO2] occurs in vegetative phase through changes in ratio of leaf area to whole plant dry weight, LAR. But, in reproductive growth phase (i.e. after initiation of panicle formation), the difference between photosynthetic response to [CO2] of population A and that of population B decreased. Although LAR of population C was almost always less than that of population A, there was no difference between the photosynthetic response to [CO2] of population A at 24 degrees C and that of population C at 26 degrees C for its whole growth period. These results are useful to make a model to predict carbon sequestration of rice community, which is an important type of vegetation especially in Asia in future global environmental change.

Carbon Dioxide↗
PubMed2001

Thermal stability and enzymatic activity of a smaller lysozyme from silk moth (Bombyx mori).

Bombyx mori lysozyme is 10 amino acids shorter than hen egg-white lysozyme, which is a typical c-type lysozyme. It was expressed by using the methylotrophic yeast Pichia pastoris. The thermal stability and the enzymatic activity of the Bombyx mori lysozyme were estimated and compared with those of human and hen egg-white lysozymes. The denaturation temperature was 17-26 degrees C lower than those of human and hen egg-white lysozymes. Further, the enthalpy change and the heat capacity change for unfolding were smaller than those of human lysozyme. It was also confirmed that the stability against guanidine hydrochloride was lower than those of the other two lysozymes. The enzymatic activity toward a simple synthetic substrate was measured and compared with those of human and hen egg-white lysozymes. The B-F binding mode was obviously dominant, although the A-E binding mode was preferred in human and hen egg-white lysozymes.

Acetylglucosamine↗
PubMed2001

High glucose stimulates hyaluronan production by renal interstitial fibroblasts through the protein kinase C and transforming growth factor-beta cascade.

Deposition of hyaluronan has been implicated in the pathogenesis of diabetic glomerulosclerosis. We hypothesized the involvement of hyaluronan in diabetic tubulointerstitial fibrosis. We investigated high-glucose effect on hyaluronan production by rat renal interstitial fibroblasts (normal rat kidney [NRK] cells) and examined the role of hyaluronan in NRK cell proliferation. The involvement of protein kinase C (PKC) and transforming growth factor-beta (TGF-beta) in this response was also examined. After 24 hours of incubation in medium containing 25.6 mmol/L glucose, production of hyaluronan by NRK cells was significantly increased compared with medium containing 5.6 mmol/L glucose (P <.01). L-glucose and mannitol had no effect on hyaluronan production. High glucose enhanced basal in situ PKC activity (P <.01), and both an activator of PKC (phorbol 12-myristate 13-acetate; [PMA]) and TGF-beta 1 were able to increase hyaluronan production by NRK cells (P <.01). The effect of high glucose on hyaluronan production was diminished by coincubating cells with PKC inhibitors (staurosporine [Stp] or calphostin C [CpC]) or with an anti-TGF-beta neutralizing antibody. Stimulation of hyaluronan production by PMA was also normalized by anti TGFbeta neutralizing antibody, but the effect of TGF-beta1 was not affected by inhibition of PKC. Finally, incubating quiescent NRK cells with 50 or 100 ng/mL hyaluronan for 24 hours significantly increased NRK cell number (P <.01). In conclusion, high glucose stimulates hyaluronan production through the PKC/TGF-beta cascade. Increased hyaluronan promotes NRK cell proliferation. These results suggest that hyaluronan may play a role in the pathogenesis of interstitial fibrosis in diabetic kidney disease.

Animals↗
PubMed2001

Energetics of three-state unfolding of a protein: canine milk lysozyme.

Thermodynamics of thermal transitions of a calcium-binding lysozyme, canine milk lysozyme (CML), was studied using differential scanning calorimetry and compared with those for homologous proteins, human alpha-lactalbumin (alpha-hLA) and equine milk lysozyme (EML). The results showed that CML and EML exhibit two clear heat absorption peaks in the absence of calcium ions (apo-form), although the cooperative thermal transition of alpha-hLA is apparently absent in this form. The first peak represents the unfolding transition from the native to an unfolding intermediate state (N-I transition) and the second peak represents that from the intermediate to the thermally unfolded state (I-U transition). We interpret that the cooperative thermal transition, which is observed between the intermediate and the thermally unfolded states of CML and EML, comes from the native-like packing interaction in their intermediate states. Furthermore, to examine the role of the stabilization mechanism of CML intermediate, we constructed four variant CMLs (H21G, I56L, A93S and V109K), in which the residues of CML are substituted for those of EML, and also investigated their thermal stability. Especially the His21 and Val109 of CML play a role in stabilization of the intermediate state and their contributions to the unfolding free energy are estimated to be 2.0 and 1.8 kJ/mol, respectively. From the results of the mutational analysis, a few differences in the local helical interactions within the alpha-domain are found to be predominant in stabilizing the intermediate state.

Animals↗
PubMed2001

Construction of an expression system of insect lysozyme lacking thermal stability: the effect of selection of signal sequence on level of expression in the Pichia pastoris expression system.

Expression systems of human and silkworm lysozymes were constructed using the methylotrophic yeast Pichia pastoris as a host. The leader sequence and its prepro peptide of alpha-factor (a peptide pheromone derived from yeast) and the native signal sequences of these lysozymes, were used as secretion signals. When the alpha-factor leader is used as the signal sequence, human lysozyme is secreted at a much higher level than is silkworm lysozyme. On the other hand, silkworm lysozyme, when its native signal is used, is secreted more efficiently than human lysozyme. Therefore, we expected that human lysozyme cDNA with a silkworm native signal would be secreted more efficiently than human lysozyme with its native signal. However, its level of expression was not increased. This result indicates that the native signal of silkworm lysozyme does not promote the secretion of the lysozyme, but rather alpha-factor leader inhibits the secretion. Silkworm lysozyme with the alpha-factor leader is so unstable that it could be easily attacked by some proteases and our findings suggest that the level of expression of heterologous protein with signal peptides and its stability are greatly affected by the selection of the appropriate secretion signal sequence.

Amino Acid Sequence↗
PubMed2001

Identification of T helper cell subsets in continuous ambulatory peritoneal dialysis patients.

BACKGROUND/AIM: End-stage renal failure induces a clinical state of immunodeficiency with a higher incidence of infections and a higher mortality due to infectious complications as compared with the normal population. A crucial element in this immune response is the development of a network of cytokines. CD4-positive T helper (Th) cells differentiate into either Th1 or Th2 cells in response to various stimuli. It is important to examine whether the impaired immune responses in patients with end-stage renal disease are due to an enhanced Th1 response or a reduced number of Th2 cells. METHOD: Using a newly developed immunofluorescence staining of intracellular cytokines for flow cytometric analysis, we studied Th subsets in 24 patients on continuous ambulatory peritoneal dialysis (CAPD). RESULTS: The proportions of Th1 cells did not differ between CAPD patients (18.7 +/- 1.8%) and controls (19.6 +/- 1.5%). Unlike Th1 cells, a significantly higher proportion of CD4 cells in CAPD patients is characterized by a Th2-type cytokine secretion pattern as compared with healthy controls: 2.9 +/- 0.8% versus 1.7 +/- 0.4%. CONCLUSION: These data demonstrate that Th cells from CAPD patients manifest a dysregulated differentiation profile characterized by a major increase in the percentage of Th2 cells and by a normal percentage of Th1 cells.

Flow Cytometry↗
PubMed2001

Soluble osteopontin and vascular calcification in hemodialysis patients.

BACKGROUND: Vascular calcification often occurs in patients with uremia. As osteopontin (OPN) is not only involved in the physiological but also the pathological calcification of tissues, OPN may be associated with the pathogenesis of aortic calcification in hemodialysis (HD) patients. METHODS: We examined the expression of OPN in atherosclerotic aortas of HD patients. In addition, we performed a prospective longitudinal study by using CT scans to detect aortic calcifications and by measuring the plasma OPN concentration by ELISA in HD patients (20 men, 16 women; mean age 55.2 +/- 21.3 years) and in healthy volunteers (18 men, 17 women; mean age 54.0 +/- 13.2 years). RESULTS: By immunohistochemical staining, OPN was abundantly localized in atherosclerotic plaques of HD patients. The macrophages surrounding the atheromatous plaques were identified as the OPN-expressing cells. We furthermore found that the concentration of soluble plasma OPN was significantly higher in HD patients as compared with the concentrations in age-matched healthy volunteers (837.3 +/- 443.2 vs. 315.1 +/- 117.4 ng/ml, p < 0.01). The OPN concentration was positively correlated with the aortic calcification index in HD patients (r = 0.749, p < 0.01). CONCLUSION: These data suggest that OPN, secreted by macrophages, plays a role in the calcification of atheromatous plaques in HD patients.

Adult↗
PubMed2001

Effect of modification of the carboxyl groups of the sialic acid binding lectin from bullfrog (Rana catesbeiana) oocyte on anti-tumor activity.

The sialic acid binding lectin from bullfrog Rana catesbeiana oocyte (cSBL) is known to have anti-tumor activity. In order to investigate the relationship between the net charge of cSBL and its anti-tumor effect, cSBL was modified with a water-soluble carbodiimide (EDC) in the presence of three kinds of nucleophiles, taurine, glycine methylester and ethylenediamine. cSBL having four carboxyl groups was partially modified (ca. 2 residues). The anti-tumor activity of modified cSBLs was in the order of ethylenediamine-modified cSBL > glycine methylester-modified cSBL > taurine modified cSBL > or = native cSBL. The results suggested that anti-tumor activity seems to increase with the increase in positive net charge, possibly enhancing the interaction of cSBL with sialoglycoprotein on the surface of tumor cells. The ribonuclease activity of ethylenediamine-modified cSBL decreased with the progress of the reaction, but the number of internalized molecules in the tumor cell increased. Thus, for antitumor activity, a higher incorporation of cSBL with reasonable RNase activity seems to be more important than total RNase activity.

Amino Acid Sequence↗
PubMed2001

Analysis of lupus activity in end-stage renal disease treated by hemodialysis.

OBJECTIVE: The activity of systemic lupus erythematosus (SLE) has been reported to decrease in patients who have developed end-stage renal disease (ESRD). However, extrarenal symptoms attributable to the disease activity are noted, especially during the first year of dialysis. We studied the clinical course and evaluate the disease activity of SLE in patients with ESRD on hemodialysis for more than 6 months. SUBJECT AND METHODS: Fourteen patients with SLE who had been initiated on maintenance dialysis at our center between 1982 and 1999 were examined retrospectively. Their clinical details, organ system manifestations, serologic profiles and immunosuppressive treatment regimens were reviewed. Patients with and without postdialysis flaras of SLE were compared statistically. RESULTS: Five patients exhibited 6 SLE flares under treatment with corticosteroids. Two flares occurred within the first year of the initiation of dialysis, and in 1 patient, aggravation of the disease activity was noted 98 months after the initiation of dialysis. Polyarthritis was noted in 5 cases and fever in 4 cases. The serum complement levels decreased in all 6 cases with relapse of SLE activity. Compared with the other 9 patients who did not exhibit SLE relapse, no significant differences were found in 5 patients who did with respect to the demographic and serologic features at the initiation of dialysis. CONCLUSION: We conclude that the disease activity does not always burn out in patients of SLE who show progression to ESRD. SLE flares can sometimes occur even after one year of the initiation of dialysis. SLE patients on dialysis should be carefully followed up by clinical and serological monitoring, and treated by appropriate immunosuppressive therapy.

Adolescent↗