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Biomedical subjects

F Watanabe

Publications and source records attributed to F Watanabe.

At least 163 records · Page 9Linked to original sources
PubMed1993

Corrinoid specificity of cytosolic cobalamin-binding protein of Euglena gracilis z.

To elucidate the corrinoid specificity of the cytosolic cobalamin-binding protein of Euglena gracilis, inhibition of the binding of radioactive cyanocobalamin to the cytosolic binding protein was studied with a variety of cobalamin analogues. The cytosolic cobalamin-binding protein showed an absolute requirement for the alpha-axial ligand (the cobalt-coordinated nucleotide) in cobalamin binding, but was not able to recognize certain differences in the base or ribose moiety. Regarding the contributions of the b-, d-, and e-propionamide side chains in the binding of cobalamin to the cytosolic protein, the order of the contributions was shown to be b > d > e; in particular the b-propionamide side chain was essential for the formation of the protein-cobalamin complex. No involvement of the beta-axial ligand or the alkanolamine group in the binding of cobalamin to the protein was found.

Animals↗
PubMed1993

Uptake of cobalamin by Euglena mitochondria.

Cobalamin uptake by Euglena mitochondria is a biphasic process, consisting of energy-independent cobalamin-binding to mitochondrial membranes and energy-dependent active transport. The energy-dependent phase of cobalamin uptake is not dependent on mitochondrial respiration, but on the presence of ATP within the mitochondrial matrix. The dissociation constant of the energy-independent cobalamin-binding reaction is estimated to be 0.45 nM. Inhibition of the mitochondrial cobalamin uptake by a variety of cobalamin analogues indicates that Euglena mitochondria have an absolute requirement for the complete cobalamin molecule with an alpha-axial ligand (the cobalt-coordinated nucleotide) and an intact b-propionamide side-chain. Thus, the Euglena mitochondrial cobalamin uptake system is highly specific for the cobalamin structure. The cobalamin taken up by the Euglena mitochondria cannot be exchanged with exogenous cobalamin. All of the mitochondrial cobalamin is associated with three proteins with molecular masses of > 700,000 (16.3%), 160,000 (7.4%), and 35,000 (76.3%). They occur in the soluble fraction of mitochondria, suggesting that these cobalamin-binding proteins or cobalamin-dependent enzymes play an important role in cobalamin accumulation and metabolism within the mitochondria.

Adenosine Triphosphate↗
PubMed1993

[Investigation on immunological factors of non- and low-responders to hepatitis B vaccine].

We investigated the immunological factors concerning the backgrounds of non- and low-responders who could not respond well to the hepatitis B (HB) vaccine. We injected 10 micrograms of the recombinant HB vaccine to the medical staffs of our hospital intramuscularly three times, 199 subjects of whom could receive the full course of immunization with the HB surface (HBs) antigen. We found that 14 subjects were non-responders whose titer of HBs antibody was under the 1.9 cut off index (C.I.) examined by radioimmunoassay (RIA) and 47 ones were low-responders whose titers were between 2.0 to 9.9 C.I. and the frequency of non- and low-responders was higher in males after the full course of HB vaccination. We chose 46 subjects and divided them into 4 groups according to the titer of HBs antibody at 8 and 28 weeks. We compared those groups to each other according to the amounts of total protein, gamma-globulin, IgG, IgA and IgM, numbers of peripheral white blood cells and lymphocytes, and percentages of peripheral lymphocyte and subsets of T cell including the examination by two-color flow cytometry using monoclonal antibodies. However we could not get any significant difference in any of those immunological factors by T assay. From these findings we suggest that the response to the HB vaccine does not depend on the quantity of the immunological factors before vaccination but on specific reactivity to HBs antigen after vaccination.

Adult↗
PubMed1993

Characteristics of mass fragmentation of steroids by atmospheric pressure chemical ionization-mass spectrometry.

The characteristics of the mass spectra of sixty steroids were investigated using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). In APCI-MS, the drift voltage and nebulizer temperature affected the appearance of molecular ions. Solvent adducted ions [M+H+CH3CN]+ and [M+H+H2O]+ were decreased with an increase in drift voltage. The optimum drift voltage differed slightly for each steroid. These sixty steroids were divided into two groups according to their mass spectra profiles: one having a carbonyl group at position 3 together with a double bond at position 4 (group A) and the other bearing a hydroxyl group at the 3 position (group B). In group A, the predominant peak observed corresponded to the protonated molecular ion [M+H]+. The fragment ion corresponding to the elimination of CH2OH, COCH3 and/or COCH2OH from the steroid skeleton appeared as a base peak in some steroids of group A. In group B, predominantly [M+H-H2O]+ and/or [M+H-2H2O]+ ion(s), originating from the loss of water molecules, were observed. Other major ions in this group were the protonated molecular ions. Like other chemical ionization mass spectrometry, the mass spectrum of each steroid was very simple. These results suggest that APCI-MS is a suitable tool for the determination of the mass number of polar, nonvolatile and thermolabile steroids without derivatization.

Chromatography, High Pressure Liquid↗
PubMed1993

Effects of volume loading, propranolol, and heart rate changes on pump function and systolic time intervals of the left atrium in open-chest dogs.

Left atrial (LA) pressure-dimension curve was constructed and the area of A-loop (AAL, in mm.mmHg) which reflected LA stroke work was measured in 14 open-chest dogs before and after saline infusion, in 14 dogs before and after propranolol administration under fixed heart rate and in 12 dogs while atrial pacing rate was increased stepwise. The peak +dP/dt of LA systolic pressure (LA +dP/dt, in mm Hg/s) and LA percent fraction shortening (LA %FS) were obtained as indices of LA pump function. The peak -dP/dt of X descent in LA pressure (LA -dP/dt, in mm Hg/s) was measured as an index of LA relaxation. From pulsed Doppler mitral flow velocities, A-wave acceleration (AC, in cm/s2), LA pre-ejection period corrected by P-wave duration (LA PEPc), and LA ejection time (LA ET) were measured. AAL, LA +dP/dt, AC, LA %FS, and LA -dP/dt increased after saline infusion (AAL; 2.2 +/- 1.6 to 5.1 +/- 3.3 (p < 0.05), LA +dP/dt; 34 +/- 16 to 52 +/- 23 (p < 0.05), AC; 320 +/- 90 to 472 +/- 98 (p < 0.05), LA %FS; 9 +/- 4 to 12 +/- 4 (p < 0.05), and LA -dP/dt; 38 +/- 28 to 60 +/- 32 (p < 0.05)) and decreased after propranolol administration (AAL; 2.9 +/- 1.9 to 1.2 +/- 0.7 (p < 0.05), and LA +dP/dt; 42 +/- 19 to 28 +/- 11 (p < 0.05), AC; 332 +/- 92 to 254 +/- 102 (p < 0.05), LA %FS; 14 +/- 5 to 8 +/- 5 (p < 0.05), and LA -dP/dt; 36 +/- 19 to 26 +/- 18 (p < 0.05)), but did not change significantly during heart rate increments. LA PEPc decreased after saline infusion (114 +/- 11 to 104 +/- 14 (p < 0.05)) and increased after propranolol administration (108 +/- 8 to 129 +/- 13 (p < 0.05)). As pacing rate was increased, LA PEPc and LA ET showed no significant changes. Both AAL and LA +dP/dt correlated significantly with LA PEPc (r = -0.76 and -0.66), but not with LA ET (r = -0.08 and -0.04). In conclusions, LA pump function was augmented by volume loading and decreased by propranolol, but unchanged by heart rate increments. These changes in LA pump function were reflected by LA PEPc, but not by LA ET. LA PEPc is a useful index of LA pump function which is not heart rate dependent.

Animals↗
PubMed1993

The effect of fructose on fructose 2,6-bisphosphate level and fructose 6-phosphate, 2-kinase activity in the perfused rat liver.

In order to investigate the effect of fructose on the metabolic rates of liver glycolysis, changes in fructose 2,6-bisphosphate content and fructose 6-phosphate, 2-kinase (F6P2kinase) activity were examined using perfused rat liver. When the starved liver was perfused with 0.5 mM fructose, the fructose 2,6-bisphosphate level was 6.66 nmol/g liver, or the maximum. However, with further increases in the fructose concentration, increments in the fructose 2,6-bisphosphate level gradually decreased. F6P2kinase was inactive in the starved rat liver. By perfusion with the medium containing fructose or even without fructose, however, the enzyme was activated. The suppression of the increase in the fructose 2,6-bisphosphate level by perfusion at higher fructose concentrations was at least partly due to the inhibition of F6P2kinase by F1P.

Adenosine Triphosphate↗
PubMed1993

[S-phase fraction and malignant potential in DNA diploid colorectal cancer].

Patients with DNA diploid tumor have a significantly longer survival than those with DNA aneuploid in colorectal cancer, but some patients with diploid tumor show poor survival. For assessing malignant potential in diploid colorectal cancer, flow cytometric analysis of S-phase fraction (SPF) was investigated using paraffin-embedded materials from 79 carcinoma patients who had been treated from 1971 to 1989. There was no significant correlation between SPF and clinicopathological factors (such as sex, tumor size, tumor location, macroscopical type, depth of invasion, node metastasis, peritoneal dissemination, liver metastasis and clinical stage). Mean SPF was significantly higher in poorly differentiated type carcinomas than in well differentiated type carcinomas. Patients with higher SPF had a tendency to poorer survival than those with lower SPF. From these results, it was concluded that SPF represents histological differentiation and that SPF may be a prognostic indicator, in diploid colorectal cancer.

Carcinoma↗
PubMed1993

[Development of multiple subcutaneous nodules in a patient with rheumatoid arthritis during methotrexate therapy].

A 59-year-old woman with a 14 years' history of seropositive nodular rheumatoid arthritis (RA) who developed multiple subcutaneous nodules during methotrexate therapy was reported. Weekly pulse methotrexate therapy (5-7.5 mg) was initiated in June, 1990 for exacerbation of RA. By January 1991 (total dose of methotrexate: ca 240-310 mg), marked clinical and laboratory improvements were observed. However, subcutaneous which were present prior to methotrexate administration, increased in number and size. The excised nodules showed typical histological features of rheumatoid nodules. The subcutaneous were also characterized by their presence in atypical locations such as the extensor surfaces of finger joints and toes. Recent reports which describe development of subcutaneous nodules and vasculitic lesions in RA patients following methotrexate therapy indicate different pathogenetic mechanisms might be involved in articular disease and nodular lesions.

Arthritis, Rheumatoid↗
PubMed1992

NADPH-cytochrome c (P-450) reductase has the activity of NADPH-linked aquacobalamin reductase in rat liver microsomes.

To elucidate the mammalian system for synthesis of cobalamin coenzymes, microsomal NADPH-linked aquacobalamin reductase was purified and characterized. The enzyme was purified about 534-fold over rat liver microsomal fraction in a yield of about 32%. The purified enzyme was homogeneous in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and had a monomeric molecular weight of 79,000. The purified aquacobalamin reductase showed a high specific activity (about 55 mumol/min per mg protein) of NADPH-cytochrome c (P-450) reductase. About 33% of the NADPH-cytochrome c reductase activity found in the microsomal fraction was recovered in the final purified preparation. The activity ratio of NADPH-cytochrome c reductase/NADPH-linked aquacobalamin reductase was about 5.0 through the purification steps, indicating that the rat liver microsomal NADPH-linked aquacobalamin reductase is the NADPH-cytochrome c reductase.

Animals↗
PubMed1992

Enzyme immunoassay for serum dexamethasone using 4-(carboxymethylthio)dexamethasone as a new hapten.

A sensitive and simple enzyme immunoassay for direct quantitation of serum dexamethasone was established. An antiserum with high specificity was produced by the immunization of rabbits with a newly synthesized 4-(carboxymethylthio)dexamethasone-bovine serum albumin conjugate. Alkaline phosphatase was used as a labeling enzyme. The minimum amount of dexamethasone detected was 2 pg per tube on the basis of B/Bo 100 - 2 SD (%) of standard curve. However, taking into account the cross-reaction with steroids such as cortisol in dexamethasone-free serum, the measurable range was from approximately 0.13 to 10 micrograms/dl. Intra- and interassay coefficients of variation were 1.5 - 5.4% and 0.6 - 6.5%, respectively. Serum levels of dexamethasone and cortisol in four normal subjects after an oral administration of 1 mg of dexamethasone are also reported.

Animals↗
PubMed1992

Cytochrome b5/cytochrome b5 reductase complex in rat liver microsomes has NADH-linked aquacobalamin reductase activity.

To study the mammalian system for synthesis of cobalamin coenzymes, rat liver microsomal NADH-linked aquacobalamin reductase was characterized. Microsomal NADH-linked aquacobalamin reductase, which was solubilized with 10 g/L sodium deoxycholate, showed identical elution behavior to NADH-cytochrome c reductase (cytochrome b5/cytochrome b5 reductase complex) on DEAE-Toyopearl 650 column chromatography. By mixing the purified cytochrome b5 with cytochrome b5 reductase, cob(II)alamin was immediately formed from aquacobalamin and NADH. These results provide evidence that the NADH-linked aquacobalamin reductase activity is derived from the cytochrome b5/cytochrome b5 reductase complex in rat liver microsomes. Some properties of the cytochrome b5/cytochrome b5 reductase complex in the form of NADH-linked aquacobalamin reductase were studied. The inhibition studies with cobalamin analogues suggested that hydrophobicity of the corrin ring of cobalamin molecule is involved in binding of cobalamin to the cytochrome b5/cytochrome b5 reductase complex.

Animals↗
PubMed1992

Heat distribution in bone during preparation of implant sites: heat analysis by real-time thermography.

The purpose of this experiment was to observe and measure the distribution of heat to bones and the maximum temperature that developed when cutting bone with drills. Generation of heat that spread in the presence or absence of irrigation when drilling with IMZ, Brånemark, and ITI implant (F type) drills was observed in the pig rib via thermography. Without irrigation, the condition of heat spread in each drill and bur differed according to bur shape and drilling site. Maximum heat temperature without irrigation was higher than that with irrigation for any IMZ, ITI, and Brånemark drill.

Animals↗
PubMed1992

[Improvement of pancytopenia and articular and by splenectomy in a patient with Felty's syndrome].

A forty seven year-old woman with a 18 years history of rheumatoid arthritis presented with recurrent infection and pancytopenia. A diagnosis of Felty's syndrome was made hand on clinical and laboratory findings. In spite of drug therapy using nonsteroidal anti-inflammatory drugs, D-penicillamine and corticosteroid, the hematological abnormalities and active joint symptoms continued. Recurrences of severe bacterial infection and the rupture of esophageal varices necessitated splenectomy. Soon after the operation, dramatic improvement of hematological abnormalities were observed. Furthermore, after 3 months postoperatively, marked decrease in rheumatoid activities and disappearance of subcutaneous nodules were noticed. Titer of rheumatoid factor also showed a significant reduction and became negative 6 months after the operation. Although the efficacy of splenectomy on hematological abnormalities in Felty's syndrome has been well documented, its effect on rheumatic disease has not been clarified. The case presented here might suggested that suppression of reticuloendothelial system may have therapeutic effects in rheumatoid arthritis. The possible mechanisms involved in these findings have been discussed.

Felty Syndrome↗
PubMed1991

Vitamin B12 metabolism in a photosynthesizing green alga, Chlamydomonas reinhardtii.

To elucidate vitamin B12 (cobalamin) metabolism in green algae, Chlamydomonas reinhardtii was labeled with radioactive cobalamin for 4 days. The Chlamydomonas cells did not require cobalamin for growth, but nevertheless took up and accumulated exogenous cobalamin. The level of the accumulated cobalamin reached a maximum (about 20 fmol/10(6) cells) at day 1 of the cell growth. The cobalamin accumulated by the 4-day cells was partly converted to the coenzymes (5'-deoxyadenosylcobalamin, 20.7% and methylcobalamin, 4.8%). The cells contained NADH- and NADPH-linked aquacobalamin reductases (35.9 and 31.5 nmol/min per mg protein, respectively) involved in the synthesis of the coenzymes. Most of the accumulated cobalamin was associated with two heat-labile macromolecules; the coenzymes synthesized were recovered in the macromolecular fraction with a molecular weight of 230,000, while non-coenzyme forms (cyanocobalamin and hydroxocobalamin) predominated in that with a molecular weight of 40,000. Evidence for de novo biosynthesis of cobalamin was also obtained in the alga, indicating that it has both ability to synthesize cobalamin and take up the exogenous vitamin.

Chlamydomonas↗
PubMed1991

Vitamin B-12 deficiency increases the specific activities of rat liver NADH- and NADPH-linked aquacobalamin reductase isozymes involved in coenzyme synthesis.

Rat liver contains both NADH- and NADPH-linked aquacobalamin reductases, which are involved in the synthesis of the vitamin B-12 coenzymes and are distributed in both the mitochondrial and microsomal membranes. To clarify the physiological roles of these hepatic enzymes, vitamin B-12-deficient rats were used to study the effect of the deficiency on the enzyme activities. Male rats fed a vitamin B-12-deficient diet for 11 wk developed a severe vitamin B-12 deficiency with a high urinary methylmalonate excretion (214.3 +/- 115.2 mumol/d) and approximately 96% lower hepatic vitamin B-12 content. Tissues of the vitamin B-12-deficient rats were assayed for NADH- and NADPH-linked aquacobalamin reductase activities. The specific activities of both enzymes in homogenates of liver, kidney or upper intestine were shown to be three- to 20-fold greater in the vitamin-deficient rats than in the control rats. In liver, the vitamin deficiency specifically elevated the specific activities of the mitochondrial NADH-linked and microsomal NADPH-linked enzymes. These are likely the isozymes involved in vitamin B-12 coenzyme synthesis.

Animals↗