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T Niwa

Publications and source records attributed to T Niwa.

At least 73 records · Page 4Linked to original sources
PubMed1999

Gas chromatographic-mass spectrometric analysis of erythrocyte 3-deoxyglucosone in hemodialysis patients.

The erythrocyte levels of 3-deoxyglucosone (3-DG) were measured by a selected ion monitoring method of gas chromatography-chemical ionization mass spectrometry using [13C6]-3-DG as an internal standard. Because the erythrocyte levels of 3-DG measured after deproteinization using ethanol were 18 times higher than those using ultrafiltration, we used ethanol deproteinization for measurement of total 3-DG in the erythrocytes. The concentration of 3-DG was significantly elevated in hemodialysis (HD) patients compared with healthy subjects. Although HD treatment could remove the erythrocyte 3-DG efficiently, its post-HD levels were still elevated compared with the healthy subjects.

Aged↗
PubMed1999

Experimental induction of AGEs in fetal L132 lung cells changes the level of intracellular cathepsin D.

The effect of the carbonyl compound glyoxal on the induction of advanced glycation end products (AGEs) in the fetal epithelial lung cells L132 was investigated using immunohistochemical, immunoelectron microscopic, and biochemical methods. It was found that glyoxal treatment resulted in morphological changes of the cells and in the membranous and cytosolic localization of AGEs such as methyl-glyoxal-derived compounds, N-(carboxymethyllysine) (CML) and imidazolone. The formation of AGEs was accompanied with a change in the intracellular expression of cathepsin D and a loss of enzymatic activity.

Antibodies↗
PubMed1999

Preventive effect of topical vitamin E-containing liposome instillation on the progression of galactose cataract. Comparison between 5-week- and 12-week-old rats fed a 25% galactose diet.

The preventive effect of topical vitamin E-containing liposome instillation on the progression of galactose cataract was compared between 5-week- and 12-week-old Wistar rats fed a 25% galactose diet. Vitamin E-containing liposomes [LP(+VE)] and vitamin E-free liposomes [LP(-VE)] were prepared with dipalmitoylphosphatidylcholine and dioleoylphosphatidylcholine (7:3 w/w). Twice daily instillation of either LP(-VE) or LP(-VE) into both eyes of 5-week-old rats fed the galactose diet for 18 days (5WGR) and 12-week-old rats fed the galactose diet for 7 weeks (12WGR) at which time some vacuoles appeared in the lens cortical equator, was conducted for a period of 4 and 9 weeks, respectively. The severity of cataracts at the end of instillation was similar in 5WGR and 12WGR. Instillation of LP(+VE), but not LP(-VE), retarded cataract progression in 5WGR and 12WGR. In 12WGR, LP(-VE) instillation caused a transient retardation of the progression. In lenses of 5WGR and 12WGR, decreases in vitamin E and reduced glutathione contents and increases in lipid peroxide, galactitol, and water contents occurred at the onset of instillation. For 5WGR, a decrease in lens reduced glutathione content and increases in lens vitamin E, lipid peroxide, galactitol, and water contents occurred at the end of instillation. For 12WGR, decreases in lens reduced glutathione and vitamin E contents and increases in lens lipid peroxide, galactitol, and water contents occurred at the end of instillation. In sera of 5WGR and 12WGR, vitamin E concentration decreased at the onset of instillation increased at the end in 5WGR and was unchanged in 12WGR. In 5WGR, instillation of LP(+VE), but not LP(-VE), for 4 weeks prevented these changes except the changes in lens galactitol and water contents and serum vitamin E concentration. In 12WGR, instillation of LP(+VE), but not LP(-VE), for 9 weeks prevented these changes except the changes in lens galactitol and water contents and serum vitamin E concentration. These results indicate that topically instilled LP(+VE) can retard cataract progression in 5WGR and 12WGR, mainly by the antioxidative action of vitamin E contained in the instilled liposomes.

Animals↗
PubMed1999

Differential accumulation of advanced glycation end products in the course of diabetic retinopathy.

AIMS/HYPOTHESIS: Glycated proteins, formed by reaction of glucose and protein, react further yielding numerous, mostly undefined advanced glycation end products (AGE). The recently characterized imidazolone-type AGE (AG-1) is non-oxidatively formed involving 3-deoxyglucosone whereas some AGEs, particularly N(epsilon)-(carboxymethyl)lysine (CML), are formed only in the presence of oxygen. METHODS: To study the possible contribution of oxidative and non-oxidative AGE formation in the development of diabetic retinopathy antibodies directed against CML-type and imidazolone-type AGEs were characterized by dot blot analysis and used to localize these well-characterized epitops in the retinas from diabetic rats (early course) and from human Type I (insulin-dependent) diabetes mellitus with laser-treated proliferative diabetic retinopathy (late course). RESULTS: In non-diabetic rats CML was moderately positive in neuroglial and vascular structures of non-diabetic rat retinas and increased strongly in diabetic retinas. Anti-imidiazolone antibody staining was strongly positive only in diabetic capillaries. Advanced human diabetic retinopathy showed strong CML-immunolabelling of the entire retina whereas control samples showed moderate staining of neuroglial structures only with the polyclonal CML-antibody. Anti-imidiazolone antibody staining was faint in the inner retina of control sections but were strong throughout the entire diabetic retina. Immunolabelling for the AGE-receptor was congruent with a marker of Müller cells. CONCLUSION/INTERPRETATION: Our data indicate that the oxidatively formed CML is present in non-diabetic retinas as a regular constituent but increases in diabetes both in neuroglial and vascular components. Imidazolone-type AGE are restricted to microvessels and spread during later stages over the entire retina, co-localizing with the expression of AGE-receptor.

Animals↗
PubMed1999

Dose escalation and pharmacokinetic study of a humanized anti-HER2 monoclonal antibody in patients with HER2/neu-overexpressing metastatic breast cancer.

We conducted a phase I pharmacokinetic dose escalation study of a recombinant humanized anti-p185HER2 monoclonal antibody (MKC-454) in 18 patients with metastatic breast cancer refractory to chemotherapy. Three or six patients at each dose level received 1, 2, 4 and 8 mg kg(-1) of MKC-454 as 90-min intravenous infusions. The first dose was followed in 3 weeks by nine weekly doses. Target trough serum concentration has been set at 10 microg ml(-1) based on in vitro observations. The mean value of minimum trough serum concentrations at each dose level were 3.58 +/- 0.63, 6.53 +/- 5.26, 40.2 +/- 7.12 and 87.9 +/- 23.5 microg ml(-1) respectively. At 2 mg kg(-1), although minimum trough serum concentrations were lower than the target trough concentration with a wide range of variation, trough concentrations increased and exceeded the target concentration, as administrations were repeated weekly. Finally 2 mg kg(-1) was considered to be sufficient to achieve the target trough concentration by the weekly dosing regimen. One patient receiving 1 mg kg(-1) had grade 3 fever, one at the 1 mg kg(-1) level had severe fatigue defined as grade 3, and one at 8 mg kg(-1) had severe bone pain of grade 3. No antibodies against MKC-454 were detected in any patients. Objective tumour responses were observed in two patients; one receiving 4 mg kg(-1) had a partial response in lung metastases and the other receiving 8 mg kg(-1) had a complete response in soft tissue metastases. These results indicate that MKC-454 is well tolerated and effective in patients with refractory metastatic breast cancers overexpressing the HER2 proto-oncogene. Further evaluation of this agent with 2-4 mg kg(-1) weekly intravenous infusion is warranted.

Antibodies, Monoclonal↗
PubMed1999

Cloning and sequence of a cDNA for a highly basic protease from the digestive juice of the silkworm, Bombyx mori.

A serine protease of the silkworm, Bombyx mori, with an isoelectric point of pH 10-11 and a pH optimum for succinyl-Leu-Leu-Val-Tyr-MCA degrading activity of about 10, was found in a 0.33 M NaCl-eluted fraction obtained from cation-exchange chromatography of digestive juice. The activity of the enzyme was strongly inhibited by chymostatin and PMSF, indicating that the protease is a chymotrypsin-like serine protease. The N-terminal amino acid sequence of the protease was determined, and a full-length cDNA clone (0.92 kbp) which was isolated from a midgut cDNA library was sequenced. The cDNA encodes a pre-proenzyme of 284 amino acids with a pro-segment of 50 amino acids and mature protein of 234 amino acids. From its primary structure, the predicted molecular mass of the mature protein is 24.5 kDa. A sequence comparison of the Bombyx highly basic protease with other serine proteases revealed that this enzyme is a mammalian-type serine protease with a catalytic triad consisting of His45, Asp92 and Ser186. A large number of Arg residues are encoded by the cDNA which may be responsible for its stability and/or function in the alkaline condition, by remaining charged at high pH.

Amino Acid Sequence↗
PubMed1999

Increased erythrocyte 3-DG and AGEs in diabetic hemodialysis patients: role of the polyol pathway.

BACKGROUND: 3-Deoxyglucosone (3-DG) accumulating in uremic serum plays an important role in the formation of advanced glycation end products (AGEs). To determine if 3-DG is involved in the formation of intracellular AGEs, we measured the erythrocyte levels of 3-DG and AGEs such as imidazolone and N epsilon-carboxymethyllysine (CML) in hemodialysis (HD) patients with diabetes. Further, to determine if the polyol pathway is involved in the formation of erythrocyte 3-DG and AGEs, an aldose reductase inhibitor (ARI) was administered to these patients. METHODS: The erythrocyte levels of sorbitol, 3-DG, imidazolone, and CML were measured in ten diabetic HD patients before and after treatment with ARI (epalrestat) for eight weeks, and were compared with those in eleven healthy subjects. 3-DG was incubated in vitro with hemoglobin for two weeks to determine if imidazolone and CML are formed by reacting 3-DG with hemoglobin. RESULTS: The erythrocyte levels of sorbitol, 3-DG, imidazolone, and CML were significantly elevated in diabetic HD patients as compared with healthy subjects. The erythrocyte levels of 3-DG significantly decreased after HD, but sorbitol, imidazolone or CML did not. The administration of ARI significantly decreased the erythrocyte levels of sorbitol, 3-DG and imidazolone, and tended to decrease the CML level. Imidazolone was rapidly produced in vitro by incubating 3-DG with hemoglobin, and CML was also produced, but less markedly as compared with imidazolone. CONCLUSION: The erythrocyte levels of 3-DG and AGEs are elevated in diabetic HD patients. The administration of ARI reduces the erythrocyte levels of 3-DG and AGEs, especially imidazolone, as well as sorbitol. Thus, 3-DG and AGEs, especially imidazolone, in the erythrocytes are produced mainly via the polyol pathway. ARI may prevent diabetic and uremic complications associated with AGEs.

Adult↗
PubMed1999

Oral adsorbent ameliorates renal TGF-beta 1 expression in hypercholesterolemic rats.

BACKGROUND: A spontaneously hypercholesterolemic Imai rat has recently been reported as a model of focal glomerulosclerosis that causes nephrotic syndrome followed by renal failure. This study was designed to determine if an oral adsorbent, AST-120, ameliorates renal lesions and TGF-beta 1 expression in the rats. METHODS: AST-120 was given orally to the Imai rats for 32 weeks, and renal function and pathology were compared between the AST-120-administered and control Imai rats. RESULTS: AST-120-administered rats showed significantly lower level of blood urea nitrogen, serum creatinine, urinary protein, serum total-cholesterol, serum triglyceride, and serum and urinary indoxyl sulfate, and significantly higher levels of serum albumin and creatinine clearance than control rats. AST-120 reduced the glomerular sclerosis index, interstitial fibrosis area, and the extent of glomerular lipid deposition. Immunohistochemistry demonstrated that AST-120 reduced the expression of transforming growth factor (TGF)-beta 1 and tissue inhibitor of metalloproteinase (TIMP)-1 as well as interstitial infiltration of macrophages in the renal cortex of the Imai rats. CONCLUSIONS: AST-120 prevented the progression of nephrotic syndrome and renal failure in the Imai rats by ameliorating glomerular sclerosis and interstitial fibrosis, accompanied with reduced expression of TGF-beta 1 and TIMP-1, and reduced infiltration of macrophages in the kidneys.

Administration, Oral↗
PubMed1999

Contribution of human hepatic cytochrome P450s and steroidogenic CYP17 to the N-demethylation of aminopyrine.

1. Aminopyrine N-demethylase activity was determined for 11 forms of human hepatic cytochrome P450s (P450s) expressed in yeast Saccharomyces cerevisiae and for human steroidogenic CYP17 expressed in Escherichia coli. 2. Among the hepatic P450s, the N-demethylation of aminopyrine was catalysed most efficiently by CYP2C19, followed by CYP2C8, 2D6, 2C18 and 1A2, whereas the activity with CYP2E1 was negligible. The kinetics of the N-demethylation process by CYP1A2, 2C8, 2C19 and 2D6 were studied by fitting to Michaelis-Menten kinetics by Lineweaver-Burk plots. CYP2C19 exhibited the highest affinity and a high capacity for the aminopyrine N-demethylation. CYP2C8 showed the highest Vmax, followed by CYP2C19, 2D6 and 1A2, whereas the Km for CYP2C8, 2D6 and 1A2 were 10-17 times higher than that for CYP2C19. Accordingly, the Vmax/Km for CYP2C19 was more than nine times higher than that of other P450s. 3. Human steroidogenic CYP17 also catalysed aminopyrine N-demethylation and the activity was comparable with that for CYP3A4 which is a dominant P450 in human liver. The activity was increased 1.5-fold by the addition of cytochrome b5, whereas the activity was not affected by the addition of Mg2+. 4. These results suggest that several human hepatic P450s, especially CYP2C19, and steroidogenic CYP17 exhibit aminopyrine N-demethylase activity.

Aminopyrine↗
PubMed1999

Chemical analysis of melanin pigments in feather germs of Japanese quail Bh (black at hatch) mutants.

Bh (black at hatch) is a mutation of Japanese quails which causes darkening or lightening of the plumage in heterozygotes or homozygotes, respectively. We chemically analyzed melanin pigments in feather germs of Bh mutant embryos and in feathers of adult animals. Dark brown dorsal feathers of wild-type adult animals had white barrings, but heterozygous ones lacked clear barrings. The feathers of wild-type and heterozygote animals contained both eumelanins and pheomelanins, the latter being more pheomelanic. On the dorsal skin of 10-day old wild-type embryos, longitudinal stripes from black and yellow rows of feather germs developed; two or three longitudinal rows of black feather germs and then two or three rows of yellow feather germs next to the short central feather germs. Heterozygous embryos appeared black in plumage pigmentation, due to the presence of 'gray' feather germs in rows of dorsal feather germs that corresponded to yellow rows in wild-type embryos. Homozygous dorsal feather germs did not develop the black and yellow longitudinal stripes, but were brown. Chemical analysis showed that embryos of each genotype contained both eumelanins and pheomelanins in the feather germs; however, the eumelanin content in homozygous feather germs was very low. These results suggest that the Bh mutation causes pheomelanic changes in feathers of quails.

Animals↗
PubMed1999

Cataract development in 12-month-old rats fed a 25% galactose diet and its relation to osmotic stress and oxidative damage.

We attempted to clarify the pattern of cataract development in 12-month-old rats fed a 25% galactose diet and to assess the relation of cataract development with osmotic stress and oxidative damage. In lenses of 12-month-old male Wistar rats fed a 25% galactose diet over an 8-month period, suture accentuation appeared at 6 months of galactose feeding and then opacities developed from the anterior subcapsular cortex toward the posterior subcapsular cortex, reaching the nuclear region at 8 months of galactose feeding. Increases in lens galactitol and lipid peroxide contents and a decrease in lens reduced glutathione content occurred at 4, 6 and 8 months of galactose feeding. The increase in lens lipid peroxide content and the decrease in lens reduced glutathione content were accelerated with an increase in feeding period, while the increase in lens galactitol content was decelerated. An increase in lens water content and a decrease in lens protein content occurred at 6 and 8 months of galactose feeding. The lens vitamin E content increased at 6 months of galactose feeding and this increase was concomitant with increases in serum vitamin E and total cholesterol concentrations. The serum lipid peroxide concentration increased at 4 and 6 months of galactose feeding. The present results indicate that in lenses of 12-month-old rats fed a 25% galactose diet, suture accentuation appears initially and then opacities develop from the anterior subcapsular cortex toward the posterior subcapsular cortex, finally reaching the nuclear region. These results also suggest that in the galactosemic aged rats, osmotic stress would mainly contribute to cataract formation, while oxidative damage could be linked to both cataract formation and progression, although an increase in lens vitamin E content occurs during the cataract development.

Animals↗
PubMed1998

Carbohydrate malabsorption following acarbose administration.

Carbohydrate absorption was assessed during acarbose administration to investigate the actions of this drug. In 7 healthy volunteers, breath hydrogen concentration was measured at 15-min intervals after administration of 6 g of lactulose, and continued until 4 h after the breath hydrogen level exceeded its pretreatment value by > or =10 ppm, then the amount of undigested carbohydrate was calculated following administration of various doses of acarbose and Ensure Liquid. Breath hydrogen data were also obtained before and after administration of acarbose to 8 patients with Type 2 diabetes mellitus for 2 and 4 months. After administration of 50 mg of acarbose with 250 ml or 500 ml of Ensure, the mean amount of unabsorbed carbohydrate was 5.3 g and 7.7 g, respectively, while unabsorbed carbohydrate increased to 10.8 g after 100 mg of acarbose with 500 ml of Ensure. In the diabetic patients, breath hydrogen excretion decreased to 31.6% of baseline after 2 months of acarbose administration, indicating decreased carbohydrate malabsorption. Despite this, the haemoglobin A1c level remained stable after 5 months. In conclusion, the extent of carbohydrate malabsorption depended on the acarbose dose and the carbohydrate load. Although carbohydrate malabsorption decreased with continued acarbose administration, the improvement of glycaemic control was maintained.

Acarbose↗
PubMed1998

Effects of various tetrahydroisoquinoline derivatives on mitochondrial respiration and the electron transfer complexes.

We report effect of various tetrahydroisoquinoline derivatives on mitochondrial respiration and the electron transfer complexes. Generally these compounds were potent inhibitors of NADH-linked mitochondrial state 3 respiration and complex I. Presence of a phenyl group at the C1 position or oxidation of N-methylated isoquinones into N-methylisoquinolinium ion augmented the potency to inhibit mitochondrial respiration and complex I. Many of these compounds have been identified in human brains. In view of the mitochondrial and oxidative stress hypothesis, our results suggest involvement of these neurotoxins as potential causes of mitochondrial failure in Parkinson's disease.

Animals↗
PubMed1998

Separation and characterization of carboxyl-linked glucuronides of bile acids in incubation mixture of rat liver microsomes.

The carboxyl-linked 24-glucuronides of common bile acids have been identified by means of liquid chromatography (LC)/atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) in an incubation mixture with a male Wistar rat liver microsomal fraction. The authentic specimens of bile acid 24-glucuronide acetate-methyl esters were synthesized unequivocally using the Mitsunobu reaction, and the APCI-mass spectrometric properties of these glucuronide derivatives were also characterized. After incubation of common unconjugated bile acids with hepatic microsomes, glucuronides were extracted and purified with a Sep-Pak C18 cartridge and lipophilic ion exchange gel, piperidino-hydroxypropyl Sephadex LH-20, and then derivatized into the acetate-methyl esters. Subsequent resolution into alpha- and beta-isomers at the glucuronosyl linkage was attained by LC on Cosmosil 5C8 and Sumichiral OA-2500 columns using 200 mM ammonium acetate (pH 7.0)-methanol (1:4, v/v), where 24-glucuronides were monitored with characteristic positive ions [M + NH4]+. The 24-glucuronides of lithocholic, chenodeoxycholic, deoxycholic, ursodeoxycholic and cholic acid were definitely characterized, in contrast to no formation of corresponding 3-glucuronides.

Animals↗
PubMed1998

Development of a dual color enzyme-linked immunospot assay for simultaneous detection of murine T helper type 1- and T helper type 2-cells.

The enzyme-linked immunospot (ELISPOT) assay is an efficient technique for the enumeration of single cells secreting antibodies and cytokines. For simultaneous differentiation of individual cells producing interleukin-2 (IL-2) and/or interleukin-4 (IL-4) at a single cell level, a dual color ELISPOT assay has been developed. In the present system, the red spots corresponding to IL-2-secreting cells (T helper type 1, Th1 cells) were developed with a horseradish peroxidase and the amino ethyl carbazole (AEC)/H2O2. The light blue spots corresponding to IL-4-secreting cells (T helper type 2, Th2 cells) were developed with an alkaline phosphatase and the Vector blue. The mixed colored (indigo) spots corresponding to both kinds of cytokine-secreting cells (T helper type 0, Th0 cells) were developed with both substrates. With this system, we could detect the IL-2- and/or IL-4-secreting cells simultaneously in crude spleen cell preparation or purified CD4 fraction. This procedure provides a useful tool for quantitatively analyzing micro-levels of dynamic immune responses.

Animals↗
PubMed1998

Enantioselective immunoaffinity extraction for simultaneous determination of optically active bufuralol and its metabolites in human plasma by HPLC.

A combined method of immunoaffinity extraction with high-performance liquid chromatography has been developed for the enantioselective determination of bufuralol and its metabolites in human plasma. The antibodies having high affinity toward the asymmetric center at the C-1 position of bufuralol and its 1'-oxidized metabolites and low affinity to their antipodes were elicited by immunization of rabbits with immunogens, (1R)- and (1S)-1'-oxobufuralol O-carboxymethyloxime-bovine serum albumin conjugates, respectively. 0.5 ml Of the immunoaffinity adsorbent (7.6 mg.ml-1 for anti-(1S)-antibody and 28.8 mg.ml-1 for anti-(1R)-antibody) prepared by immobilization of an antibody was capable of retaining up to 1 microgram of (R)- and (S)-bufuralol and up to 500 ng of other metabolites. The adsorbates were recovered quantitatively by elution with methanol-10 mM ammonium acetate buffer (pH 5) (95:5, v/v) without any interfering peaks on the high-performance liquid chromatogram. The proposed method was evaluated to be useful for the simultaneous determination of optically active bufuralol and its metabolite in plasma with acceptable recovery and precision.

Adrenergic beta-Antagonists↗
PubMed1998

Properties of a peptide containing DL-lactide/glycolide copolymer nanospheres prepared by novel emulsion solvent diffusion methods.

Novel emulsion solvent diffusion methods in water or oil were developed to prepare the peptide (TRH and elcatonin)-loaded PLGA nanospheres, via the coprecipitation of drug and polymer in the emulsion droplets induced by the diffusion of solvent. The PLGA nanospheres prepared by the emulsion solvent diffusion method in water were unimodally dispersed particles with an average diameter of about 250 nm, whereas those prepared by the emulsion solvent diffusion method in oil and the phase separation method exhibited bimodal distribution with average diameter of about 700 and 800 nm, respectively. The content and recovery of the peptide and nanospheres prepared by the emulsion solvent diffusion method in oil were superior to those of nanospheres prepared using other methods. The drug release properties from nanospheres depended strongly on their preparation processes. The nanospheres prepared by the emulsion solvent diffusion method in oil, released the drug continuously over 14 days, the rate of which was determined by the diffusion of drug in the rigid matrix structure of the nanosphere. The drug release behavior of nanospheres prepared by the phase separation method exhibited a triphasic release pattern with an initial burst and an induction period followed by the diffusion of drug through the walls of the reservoir type nanospheres, which were produced via the phase separation of polymer deposited around the emulsion droplets of the drug.

Biocompatible Materials↗