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Biomedical subjects

N Hirayama

Publications and source records attributed to N Hirayama.

At least 19 recordsLinked to original sources
PubMed2001

Effect of chromatic aberration on contrast sensitivity in pseudophakic eyes.

OBJECTIVE: To evaluate the effect of chromatic aberrations in pseudophakic eyes with various types of intraocular lenses (IOLs). PATIENTS AND METHODS: The study included 51 eyes of 33 patients who underwent cataract surgery. The eyes were divided into 3 groups according to the material from which their IOL was made: group 1, polymethyl methacrylate; group 2, silicone; and group 3, an acrylate/methacrylate copolymer. Ten normal phakic control eyes (group 4) underwent the same examination. Best-corrected distance visual acuity and contrast sensitivity were measured under white light and monochromatic light with wavelengths of 470 nm, 549 nm, and 630 nm, with the best correction under white light. RESULTS: There were no significant differences in best-corrected visual acuity and contrast sensitivity under the 549-nm monochromatic light in any group. However, under both white multichromatic light and 470- and 630-nm monochromatic light, the mean contrast sensitivity in group 3 tended to be lower, sometimes significantly, than in the other IOL groups. CONCLUSIONS: Our results showed that longitudinal chromatic aberrations of some IOLs may degrade the quality of the retinal image. Attention must be paid to the detailed optical performance of IOL materials to achieve good visual function.

Acrylates↗
PubMed2001

Origin of Ca2+ necessary for carbachol-induced contraction in longitudinal muscle of the proximal colon of rats.

The origin of Ca2+ necessary for carbachol (CCh)-induced contraction of longitudinal muscle of the proximal colon of rats was studied. CCh induced contraction of the muscle consisting of two phases, phasic and tonic phases, with a concomitant biphasic increase in [Ca2+]i. After removal of Ca2+ from the bathing solution of the colonic segments, CCh-induced contraction was rapidly inhibited; there was almost complete inhibition 1 min after the removal. Nicardipine, a blocker of voltage-dependent calcium channel, also significantly inhibited CCh-induced contraction. On the other hand, treatment of the colonic segments with thapsigargin, an inhibitor of sarcoplasmic reticulum (SR) Ca2+-ATPase, did not significantly affect the contraction except causing a slight decrease in the rate of contraction. These results suggest that Ca> entering through voltage-dependent calcium channels, but not released from SR, is essential for CCh-induced contraction of longitudinal muscle of the proximal colon of rats. This strict dependency of the CCh-induced contraction on extracellular Ca2+ was discussed in relation to the results obtained in the fundus of rats.

Aminobenzoates↗
PubMed2001

X-ray crystallographic approach to the design of phenolic schiff base reagents for the mutual separation of lanthanoids.

A novel mutual selectivity of lanthanoids in the N,N'-bis(5-nitrosalicylidene)ethylenediamine (H2Nsalen)-KCl and N,N'-bis(5-nitrosalicylidene)-o-phenylenediamine (H2Nsaloph)-KCl extraction systems was evaluated by the X-ray analysis of similar model complexes for extracted species. Cerium(IV) complexes with N,N'-bis(5-chlorosalicylidene)ethylenediamine (H2Clsalen), N,N'-bis(salicylidene)-o-phenylenediamine (H2saloph) and N,N'-bis(3,5-dibromosalicylidene)-o-phenylenediamine (H2Br2saloph) were selected as the models. The result of the X-ray analysis suggested that [Ln(III)(Nsalen)2]- and [Ln(III)(Nsaloph)2]- are meridional type (two ligands are oriented perpendicular to each other) and sandwich type (two ligands are oriented parallel to each other), respectively. It was suggested that the selectivity of the meridional structure is superior to that of the sandwich structure in these extraction systems.

Journal Article↗
PubMed2000

Mechanism of action of aragusterol a (YTA0040), a potent anti-tumor marine steroid targeting the G(1) phase of the cell cycle.

Aragusterol A (YTA0040), isolated from the Okinawan marine sponge of the genus Xestospongia, is a potent anti-tumor marine steroid that possesses a unique structural component. This compound showed broad-spectrum anti-proliferative activity against a panel of 14 human cancer cell lines (IC(50) = 0.01-1.6 microM). P-glycoprotein-mediated, multidrug-resistant cells showed cross-resistance to YTA0040 cells, whereas cisplatin-resistant non-small-cell lung-cancer (NSCLC) sublines showed a collateral sensitivity to YTA0040. In transplantable murine tumor models, YTA0040 displayed a broad spectrum and high degree of anti-tumor activity when administered i.p. or p.o. (life span T/C = 135-234%). In P388 murine leukemia cells, YTA0040 caused dose- and time-dependent suppression of nucleic acid and protein synthesis, with protein synthesis being more potently and rapidly inhibited than nucleic acid synthesis. Flow-cytometric analysis revealed that YTA0040 blocked the entry of human NSCLC-derived A549 cells into S phase, leading to arrest in the G(1) phase of the cell cycle. Western blot analysis demonstrated that YTA0040 caused a dose-dependent decrease in the levels of expression of hyperphosphorylated pRb and cyclin A in A549 cells. The level of p53 protein expression was decreased by YTA0040 treatment. A higher concentration of YTA0040 down-regulated the levels of expression of CDK2, CDK4, cyclin D1 and cyclin E. These findings indicated that YTA0040 arrested human NSCLC cells in late G(1) phase of the cell cycle through inhibition of pRb phosphorylation. Inhibition of pRb phosphorylation by YTA0040 resulted from down-regulation of levels of expression of the CDKs and cyclins involved in the G(1)/S transition and not from induction of p53 and/or the CDK inhibitor p21.

Animals↗
PubMed2000

Molecular design of novel metal-binding oligomeric human metallothioneins.

Genes for dimeric and tetrameric human metallothionein (hMT) were designed and successfully overexpressed in Escherichia coli to generate functional oligomeric hMTs. An hMT synthesized with prokaryotic codons, a linker encoding a gly-gly-gly tripeptide, and Met-deficient hMT-II was ligated to create a dimeric hMT, from which a tetrameric hMT was then constructed. The increased molecular size of the constructs resulted in improved stability and productivity in E. coli. The oligomeric proteins formed inclusion bodies which were dissolved with dithiothreitol, and the purified apometallothioneins were reconstituted with Cd or Zn ions in a reducing condition. The oligomeric hMT proteins incubated with Cd ions showed a typical Cd-thiolate absorbance peak at 245-255 nm. The dimeric and tetrameric hMT proteins exhibited both Cd and Zn binding activities that were respectively two and four times higher than those of the hMT-II monomer protein. These novel oligomeric hMTs may be useful in bioremediation for heavy metals.

Amino Acid Sequence↗
PubMed2000

Fiber Bragg grating temperature sensor for practical use

Fiber Bragg grating (FBG) is a promising measurement technology for future sensor system applications. Little attention has been given to the FBG sensor housing, however it is important that the FBG is embedded in a conventional electrical sensor housing so that it may be installed easily in instrumentation systems. We have experimentally fabricated a practical pass-through type FBG temperature sensor which is embedded in the conventional thermocouple housing. A small radius U-turn fiber spliced to the FBG is placed inside the top of a stainless sheath. Employing a high numerical aperture fiber with polyamide recoating, we have determined that the bending loss of the small radius U-turn fiber and heat resistance is less than 0.1 dB and up to 250 degrees C respectively. The wavelength shift of this sensor due to temperature change is 10.3 pm/degrees C equal to that of general FBG. Consequently the practical use of this sensor has been confirmed.

Journal Article↗
PubMed2000

Dissection and optimization of immune effector functions of humanized anti-ganglioside GM2 monoclonal antibody.

A mouse/human chimeric monoclonal antibody (MAb) KM966, specific for the cell-surface tumor antigen ganglioside GM2, was humanized by the complementarity determining regions (CDRs) grafting method. Not only the amino acid residues in the CDRs but also several in the framework regions (FRs) were changed from the human to the murine residues. A humanized variant, huKM796H/Lm-28, containing eight and five amino acid alterations in variable light (VL) and variable heavy (VH) FRs, respectively, showed a 9-fold reduction in complement-dependent cytotoxicity (CDC) compared to the chimeric KM966, despite tight antigen binding and potent antibody-dependent cellular cytotoxicity (ADCC). Several additional variants were subsequently constructed to improve the CDC of the antibody. One of the variants, designated KM8969, which differs by three amino acids, exhibited a CDC within 3-fold of the chimeric KM966. In addition, humanized KM8969 bound GM2 antigen 1.25-fold more tightly than the chimeric KM966 and showed 5-fold higher ADCC than the chimeric KM966. These results clearly show that the humanized KM8969, having the optimized immune effector functions and theoretically minimal immunogenicity, is an ideal candidate to test the effectiveness of anti-GM2 MAb in human cancer therapy. Taken together, the results obtained here indicate that the ADCC and CDC of an antibody can be dissected independently via engineering of the antibody variable region.

Amino Acid Sequence↗
PubMed2000

Antigenic differences in the H proteins of canine distemper viruses.

Antigenic properties between new Japanese field isolates and vaccine strains of canine distemper virus (CDV) have been compared using four monoclonal antibodies (MAbs) (JD-5, JD-7, JD-11 and d-7) against the hemagglutinin (H) proteins of CDV. JD-5, JD-7 and JD-11 are newly established antibodies. Three MAbs, namely d-7, JD-5 and JD-11, reacted similarly to all the CDV strains examined. However, JD-7 reacted much more strongly with the vaccine strains and an old field isolate than the recent field isolates in immunofluorescence, radio immunoprecipitation and virus neutralization assays. These results indicate that an antigenic region in the H protein, concerned with neutralization and recognized by JD-7, has been altered in the recent field isolates.

Animals↗
PubMed1999

RESPONSIVE-TO-ANTAGONIST1, a Menkes/Wilson disease-related copper transporter, is required for ethylene signaling in Arabidopsis.

Ethylene is an important regulator of plant growth. We identified an Arabidopsis mutant, responsive-to-antagonist1 (ran1), that shows ethylene phenotypes in response to treatment with trans-cyclooctene, a potent receptor antagonist. Genetic epistasis studies revealed an early requirement for RAN1 in the ethylene pathway. RAN1 was cloned and found to encode a protein with similarity to copper-transporting P-type ATPases, including the human Menkes/Wilson proteins and yeast Ccc2p. Expression of RAN1 complemented the defects of a ccc2delta mutant, demonstrating its function as a copper transporter. Transgenic CaMV 35S::RAN1 plants showed constitutive expression of ethylene responses, due to cosuppression of RAN1. These results provide an in planta demonstration that ethylene signaling requires copper and reveal that RAN1 acts by delivering copper to create functional hormone receptors.

Alkenes↗
PubMed1999

Tyrosine kinase involvement in apamin-sensitive inhibitory responses of rat distal colon.

1. It has been suggested that pituitary adenylate cyclase activating peptide (PACAP) may be involved in the non-adrenergic, non-cholinergic (NANC) inhibitory response of longitudinal muscle of rat distal colon. In this study, we have investigated the intracellular mechanism of PACAP-induced relaxation in this muscle. 2. PACAP induced an apamin-sensitive relaxation of the longitudinal muscle. The tyrosine kinase inhibitors genistein at 10 microM and tyrphostin 25 at 30 microM, but not the cyclic AMP-dependent protein kinase inhibitor Rp-8-bromoadenosine-3',5'-cyclic monophosphorothioate at 30 microM significantly inhibited the PACAP-induced relaxation to 60% and 25% of control values, respectively. PACAP did not increase the cyclic AMP content of the muscle. 3. Tyrphostin 25 at 10 microM significantly inhibited the relaxation of longitudinal muscle induced by electrical field stimulation (EFS), to 50% of control values. Apamin at 1 microM, an antagonist of small conductance Ca2+-activated K+ channels, also inhibited the relaxation, to 42 % of control values. The inhibitory effects of tyrphostin 25 and apamin were not additive (44 % of control values). 4. PACAP induced an apamin-sensitive, slow hyperpolarization of the cell membrane of the muscle. Tyrphostin 25 at 3 microM inhibited this PACAP-induced hyperpolarization. Tyrphostin 25 at 10 microM and genistein at 10 microM inhibited the apamin-sensitive inhibitory junction potentials induced by a single pulse of EFS. 5. The PACAP-induced relaxation of longitudinal muscle occurred with a concomitant decrease in intracellular Ca2+ levels ([Ca2+]i). Tyrphostin 25 at 10 microM and apamin at 1 microM abolished these PACAP-induced responses. 6. From these findings it is suggested that the activation of tyrosine kinase is involved in PACAP-induced relaxation of longitudinal muscle from rat distal colon, 'upstream of' the activation of apamin-sensitive K+ channels.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Alteration of substrate affinity of Streptomyces cholesterol oxidase for application to the rate assay of cholesterol in serum.

The Streptomyces cholesterol oxidase (ChoA) can not be adopted for the rate assay, because the Km value of the enzyme for cholesterol is very small. The choA gene was subjected to random mutagenesis in vivo, and a mutant ChoA (designated E-ChoA) that showed altered substrate affinity was obtained by screening. The Km value of E-ChoA was approximately ten times larger than that of the wild type. Unexpectedly, the thermal stability was also improved. The amino acid substitutions of E-ChoA were identified to be the valine to glutamate at position 145, which has been previously identified as one of the thermostable mutations, and the glycine to serine at position 405. The mutational effects on the structure of E-ChoA are discussed on the basis of a three-dimensional model. E-ChoA has been successfully applied to the rate assay of cholesterol in serum.

Cholesterol↗
PubMed1999

Secretion and clearance of the mature form of adrenomedullin in humans.

In the biosynthesis of adrenomedullin (AM), glycine-extended AM, an intermediate form (iAM) processed from proAM is converted to AM[1-52]-NH2, the bioactive mature form of AM (mAM), by enzymatic amidation. We earlier showed that both molecular forms of AM circulate in human plasma. In the present study, to investigate the secretion and clearance sites of mAM and iAM in humans, we examined the plasma mAM and iAM concentrations in the femoral artery and vein (FA and FV), the aortic root and coronary sinus (AO and CS), and the pulmonary artery and capillary (PA and PC) of patients with ischemic heart disease. Plasma mAM in FV was significantly (p<0.001) higher than in FA. There also was a significant (p<0.001) step-up in the plasma mAM of the CS as compared to the AO. In contrast, plasma mAM was significantly (p<0.001) reduced in the PC as compared to the PA. However, such differences were not observed in plasma iAM levels. These findings suggest that in humans the vasculature of the lower extremities and the heart produce and secrete mAM and that the lung is a clearance site of circulating mAM.

Adrenomedullin↗
PubMed1999

Epitopes and nuclear localization analyses of canine distemper virus nucleocapsid protein by expression of its deletion mutants.

A series of nucleocapsid protein (NP)-deleted genes of the Onderstepoort strain was constructed in order to locate antigenic regions of the NP of canine distemper virus. The expression of proteins from 5'-deleted NP genes was examined in COS-7 cells by indirect immunofluorescence assay using three monoclonal antibodies (MAbs), c-5, f-5 and h-6, and a rabbit serum against NP. These MAbs reacted with two regions of NP. Amino acid residues from 1 to 80, and 337-358, were necessary and sufficient for formation of the epitopes identified by MAbs f-5 and h-6, and c-5, respectively. The proteins translated from intact or 3'-deleted genes were found to be localized in the nuclei of COS-7 cells, whereas the proteins from the 5'-deleted genes were mainly detected in the cytoplasm. These results suggested that 80 amino acid residues at the N-terminus are required for transportation of NP into the nucleus.

Animals↗