PubMed Health⌕ Search

Biomedical subjects

N Asada

Publications and source records attributed to N Asada.

At least 37 records · Page 2Linked to original sources
PubMed1997

Secretion of authentic 20-kDa human growth hormone (20K hGH) in Escherichia coli and properties of the purified product.

Using Bacillus amyloliquefaciens neutral protease gene (npr), we have constructed a secretion system of 20-kDA human growth hormone (20K hGH) in E. coli. The secretion-signal region from npr was modified inserting a fragment coding a 2Lys-5Leu cluster. In this system we found that co-expression of glutathione reductase remarkably increased accumulation level of 20K hGH in periplasm and confirmed that secreted 20K hGH was correctly processed. The recombinant 20K hGH was highly purified and subjected to analyses of physicochemical properties and biological activities which are still unclear and controversial due to difficulty in preparing the sample with authentic structure. The secreted recombinant product had authentic disulfide linkages and showed molecular weight of 20,270.5 +/- 3.7 (theoretical value, 20,269.9). The results suggest that the recombinant 20K hGH is a full agonist on rat growth promotion and lipolysis stimulation in isolated rat adipose tissues. In particular, the lipolysis-stimulating activity of 20K hGH was distinct as compared with that of 22K hGH under physiological concentration. Cell proliferation activity via prolactin-receptor in Nb-2 lymphoma was obviously low as compared with that of 22K hGH.

Amino Acid Sequence↗
PubMed1997

Genetic variants affecting phenoloxidase activity in Drosophila melanogaster.

In Drosophila melanogaster, two new variants affecting the activity of phenoloxidase were found in natural populations at Gomel in Belorussia and at Krasnodar in Russia. Prophenoloxidases, A1 and A3, in these variants had the same mobilities on native electrophoresis as the wild type. However, enzymatic activities in their activated states were much lower than in the wild type, whereas the existence of prophenoloxidase proteins was demonstrated. Egg-to-adult and relative viabilities in the variants did not decrease at temperature between 18 and 29 degrees C. Genetic analyses indicated that the genes showing the phenotype of variants are new alleles of Mox and Dox-3 on the second chromosome.

Animals↗
PubMed1997

Limb salvage using distraction osteogenesis. A classification of the technique.

We report the results of distraction osteogenesis (callotasis) for the reconstruction of extensive defects after the excision of skeletal tumours in the limbs. Bone transport was performed in ten patients (five osteosarcomas and five giant-cell tumours), shortening-distraction in three (two osteosarcomas and one Ewing's sarcoma), and distraction osteogenesis combined with an intramedullary nail to reduce the time of external fixation in six (three osteosarcomas, two chondrosarcomas, and one malignant fibrous histiocytoma). The mean length of the defects after excision of the lesion was 8.4 cm. The mean external fixation index was 39.5 days/cm for the group treated by bone transport, 34.1 days/cm for the shortening-distraction group, and 24.0 days/cm for the group treated by distraction and an intramedullary nail. Functional evaluation gave excellent results in 12 patients, good in five and fair in two. There were ten complications in 19 patients, all of which were successfully treated. We also classified reconstruction using distraction osteogenesis into five types based on the location of the defects after resection of the tumour: type 1, diaphyseal; type 2, metaphyseal; type 3, epiphyseal; type 4, subarticular reconstruction; and type 5, arthrodesis. Our results suggest that reconstruction using distraction osteogenesis provides bone which will develop sufficient biomechanical strength and durability. It is beneficial in patients with an expectation of long-term survival and in growing children.

Adolescent↗
PubMed1997

Massive autoclaved allografts and autografts for limb salvage surgery. A 1-8 year follow-up of 23 patients.

We performed 23 reconstructions with bone grafts autoclaved at 135 degrees C for 10 minutes for extensive bone defects after tumor resection. In 15 cases, the resected specimens were autoclaved and used as autografts. In 7 cases, allografts obtained from amputated extremities or cadavers were autoclaved and immediately stored at -80 degrees C prior to their use. A combination of the two was used in 1 case. The grafts were used in combination with prostheses or other forms of internal fixation. The mean follow-up was 49 (14-98) months. Incorporation of the hostgraft junction was observed radiographically after a mean of 11 (6-17) months in all cases. No recurrence due to the autoclaved bone was observed. However, 10 patients suffered complications, including infection, bone resorption, fracture and loosening of the prosthesis. In terms of Mankin's evaluation of bone grafts, 12 patients were evaluated as good or excellent. We conclude that despite the complications, autoclaved autografts and allografts are viable options for reconstruction in many countries because of the difficulty of obtaining large quantities of fresh frozen allografts.

Adolescent↗
PubMed1997

[Evaluation of bone and soft tissue lesion using 99mTc-MIBI: comparison with 201Tl and the relation to chemotherapeutic effect].

Thirty-five patients with bone and soft tissue lesions were studied with 99mTc-MIBI and 201Tl to compare the uptake of two tracers. Planar images were obtained 15 min (early image) and 3 hr (delayed image) after the injection of both tracers. Images were evaluated visually and quantitatively using uptake ratio (lesion/background). In visual analysis, 23 of 35 patients showed similar uptake of both tracers, 9 showed more intense uptake of 99mTc-MIBI than 201Tl, and 3 showed more intense uptake of 201Tl than 99mTc-MIBI on early images. On delayed images, 21 of 32 patients showed similar uptake of both tracers, 3 showed more intense uptake of 99mTc-MIBI than 201Tl, and 8 showed more intense uptake of 201Tl than 99mTc-MIBI. In quantitative analysis, similar 201Tl and 99mTc-MIBI uptake ratios were obtained on early images. On delayed images, 99mTc-MIBI uptake ratios are less than that of 201Tl, but the difference was not significant. In some cases, 99mTc-MIBI accumulation was washed out on delayed images, therefore the early image is essential to evaluate 99mTc-MIBI accumulation. In all cases with the uptake ratios less than 1.20 on delayed 99mTc-MIBI images, chemotherapy was not effective. In malignant tumors, decreased uptake of 99mTc-MIBI accumulation on delayed images may indicate that chemotherapy is not effective. Delayed 99mTc-MIBI image may be a potential marker predicting chemotherapeutic effect in malignant bone and soft tissue tumors.

Adolescent↗
PubMed1995

Enhancement of LPS triggered TNF-alpha (tumor necrosis factor-alpha) production by (1-->3)-beta-D-glucans in mice.

Effects of (1-->3)-beta-D-glucans on tumor necrosis factor-alpha (TNF-alpha) production in mice in vivo were investigated with or without triggering stimulation of lipopolysaccharide (LPS). Administration of grifolan (GRN) (100-250 micrograms/mouse) obtained from Grifola frondosa, did not elevate the TNF-alpha concentration in serum, but significantly elevated LPS (10 micrograms/mouse)-elicited TNF-alpha production in serum. The priming effect was observed as early as 2 h after administration and remained high for 3 weeks. The priming effect was dependent on the strain of mice, i.e. ICR, BALB/c, and MRL/lpr (15 weeks old) showed high response. In addition, GRN administration increased membrane-bound TNF-alpha assessed by Western blotting and flow cytometry. Comparing the activity using structurally related glucans obtained from other microorganisms, highly branched glucans, SSG isolated from Sclerotinia sclerotiorum IFO 9395 and OL-2 from Omphalia lapidescence significantly increased TNF-alpha production. Small molecular weight GRN derivatives prepared by heat degradation method showed weaker priming effect. These facts suggested that the glucans showed priming effect of TNF-alpha production in vivo and that this effect was related to the degree of branching and molecular weight.

Animals↗
PubMed1994

Effects of chemical modification of arginine residues outside the active site cleft of ricin A-chain on its RNA N-glycosidase activity for ribosomes.

Ricin A-chain, a protein that inactivates ribosomes by a specific RNA N-glycosidase activity, has been shown to be inactivated by chemical modification of a few arginine residues. When two or fewer arginine residues in the A-chain were modified with [14C]phenylglyoxal, arginines at positions of 193, 196, 213, and 234/235 were found to be modified, from amino acid compositions and radioactivities of the modified peptides that were obtained by cyanogen bromide cleavage followed by tryptic and chymotryptic digestion. All these arginines have side chains outside the active site cleft; the side chain of Arg213 is adjacent to the edge of the cleft, while other modified arginines are located on the opposite side of the cleft. Kinetic analysis showed that the modification of two arginine residues caused a 8-fold loss in kcat with a 3-fold increase in Km, suggesting that this modification mainly decrease the rate of depurination with an additional effect on the affinity for ribosomes. Neither the environment of tryptophan 211 at the bottom of the cleft nor an interaction of adenine with the cleft was changed by this modification, as judged by fluorescence spectroscopy, suggesting that a conformational change of the catalytic site does not occur upon the modification. These results, taken together with other works, suggest that some of the above arginine residues outside the active site cleft may additively contribute to the catalysis of depurination and/or the initial formation of the A-chain/ribosome complex.

Adenine↗
PubMed1993

Simulation studies of data classification by artificial neural networks: potential applications in medical imaging and decision making.

Artificial neural networks are being investigated in the field of medical imaging as a means to facilitate pattern recognition and patient classification. In the work reported here, the effects of internal structure and the nature of input data on the performance of neural networks were investigated systematically using computer-simulated data. Network performance was evaluated quantitatively by means of receiver operating characteristic analysis and compared with the performance of an ideal statistical decision maker. We found that the relatively simple neural networks investigated in this study can perform at the level of an ideal decision maker. These simple networks were also found to learn accurately even when the training data are extremely unbalanced with respect to the prevalence of actually positive cases and to differentiate input data patterns by recognizing their unique characteristics.

Computer Simulation↗
PubMed1993

Activation of prophenoloxidase with 2-propanol and other organic compounds in Drosophila melanogaster.

Activation with 2-propanol and other organic compounds of prophenoloxidase purified from pupae of Drosophila melanogaster was analyzed. A1, one of the two isozymes of the prophenoloxidase, could be activated with both an endogenous activating system and artificial organic compounds including alcohols. A1 was activated within 2 min after addition of 2-propanol. The phenoloxidase activity of A1, which had been activated with 2-propanol, decreased gradually by lowering the concentration of 2-propanol taking c 60 min to attain a low level, and the activity could be re-elevated at the re-introduction of 2-propanol. Thus the reversibility of the activation of A1 in response to the change of the concentration of 2-propanol in the activating mixture could be observed. Optimum concentration of 2-propanol for the rate of activation was 50%, optimum temperature was 30 degrees C and optimum pH was 7.5. The final level of the phenoloxidase activity, which had been activated with 2-propanol, was higher than that activated with the endogenous activating system. The activated state of A1 showed properties of a tyrosinase-type phenoloxidase. The results suggested that the activation of A1 with 2-propanol is caused by the reversible conformational change of the prophenoloxidase molecule.

1-Propanol↗
PubMed1993

Purification and characterization of prophenoloxidases from pupae of Drosophila melanogaster.

Two isoforms of prophenoloxidase were isolated from pupae of Oregon-R strain of Drosophila melanogaster. The purification procedure included ammonium sulfate fractionation, Sephacryl S-200 gel chromatography, DEAE-cellulose, and hydroxylapatite column chromatography. The two isoforms, A1 and A3, could be separated by ammonium sulfate fractionation. The isoelectric points of A1 and A3 were determined to be pH 5.8 and 6.7, respectively. The molecular weights of the monomers of A1 and A3 were estimated by SDS-PAGE to be 78 and 77 kDa, respectively. The native states of A1 and A3 are considered to be homodimeric, as judged by gel-filtration chromatography.

Ammonium Sulfate↗
PubMed1993

Genetic polymorphism of prophenoloxidase A1 in Drosophila melanogaster.

Electrophoretic variations of prophenoloxidase were obtained from natural populations of Drosophila melanogaster. A1, one of the 2 isoforms of the prophenoloxidases, is polymorphic: 10 fast-migrating and 2 slow-migrating types were found in polyacrylamide gel electrophoresis among 271 wild strains. The majority were the intermediate-migrating type. By use of these variants, A1 gene was mapped at 79.6 on the right arm of the second chromosome. By deletion mapping, its cytological position was located at 55A-B. In the electropherograms, hybrids between the types differing in mobility exhibited 3 bands, indicating that A1 is a dimeric protein. The gene for A1 is expressed through larval, pupal and adult stages.

Animals↗
PubMed1990

Potential usefulness of an artificial neural network for differential diagnosis of interstitial lung diseases: pilot study.

An artificial neural network approach was applied to the differential diagnosis of interstitial lung diseases. The neural network was designed to distinguish between nine types of interstitial lung diseases on the basis of 20 items of clinical and radiographic information. A data base for training and testing the neural network was created with 10 hypothetical cases for each of the nine diseases. The performance of the neural network was evaluated by means of receiver operating characteristic analysis. The decision performance of the neural network was high; it was comparable to that of chest radiologists and superior to that of senior radiology residents. The preliminary results strongly suggest that the neural network approach has potential utility in the computer-aided differential diagnosis of interstitial lung diseases.

Computer Simulation↗
PubMed1990

[Pathophysiological analysis of cardiac function by computer processing of echocardiograms].

Automatic image processing system has been developed for analysis of cardiac function with echocardiograms. Echograms of apical long axis view were transferred to microcomputer system and processed to display three dimensional images of left ventricular myocardium. With this technology, analysis of left ventricular wall thickness in three dimensional manner revealed pathophysiological changes in ischemic heart disease.

Coronary Disease↗
PubMed1988

A new method of three dimensional analysis of left ventricular wall motion.

The three dimensional (3D) shape of left ventricles (LV) was reconstructed from gated blood pool emission computed tomography (GECT) to assess regional LV wall motion. The 3D LV shape was created using LV boundaries detected by a threshold method. Based on the length from each LV boundary to the end diastolic LV center of mass, regional percent shortening and phase of the first harmonic by Fourier analysis were calculated to create 3D functional images. These images clearly demonstrated the 3D extent of wall motion abnormality. In addition, the same 3D analysis was applied to biplane X-ray left ventriculography (LVG) by assuming that LV short axis sections were elliptic. Results of planar imaging, 3D analysis of GECT, 3D analysis of LVG and conventional LVG findings correlated well with each other. The 3D analysis of GECT is useful for non invasive quantitative analysis of LV wall motion.

Adult↗
PubMed1988

Formation and the inhibition of reaction plug in mated Drosophila--study of a primitive defense reaction.

Formation and inhibition of a reaction plug in the course of insemination reaction in Drosophila (Diptera) were investigated. When the reaction plug was formed in the vagina, fecundity was significantly reduced in interspecific crosses although the reaction plug did not affect the oviposition in intraspecific crosses. Some phenoloxidase blockers were found to be the effective inhibitors. The formation of the reaction plug was likely to be the consequence of polymerization and/or conformational change(s) of phenol-containing substance(s) involving nearly the same course of the melanization cascade reaction studied as a self-defense system in other insects.

Animals↗
PubMed1988

Left ventricular image processing of 2-D echocardiograms and 3-D reconstruction of the left ventricle.

Image processing systems of echocardiograms are discussed. The left ventricular boundary on every 2-D echocardiogram on consecutive frames digitized with an ECG (electrocardiogram) signal is traced automatically after initial manual drawing of the boundary on an end diastolic image. Various cardiac parameters are derived from these left ventricular boundaries over a cardiac cycle: volume change, regional wall motion, percentage shortening of regional wall and so on. 3-D shapes of the left ventricle and myocardium are reconstructed from several sequences of cross-sectional echo data. Cardiac parameters are also derived from these 3-D shapes and are shown on 3-D shapes as functional images of 3-D left ventricle.

Echocardiography↗
PubMed1987

New modified activated partial thromboplastin time and prothrombin time methods using a synthetic chromogenic substrate in combination with diazotization.

A chromogenic substrate, H-D-Phe-Pip-Arg-pNA (S-2238) is a highly specific substrate to thrombin and releases p-nitroaniline (pNA) by the action of thrombin. We describe new modified APTT and PT methods using S-2238 in combination with the diazotization of pNA. In the modified APTT method, 100 microliter citrated plasma (diluted to 10-fold), 90 microliter 1 mM S-2238, 100 microliter 20 mM CaCl2 and 100 microliter Actin were mixed in an ice-bath, then incubated for 8 min at 37 degrees C. The reaction was stopped, and the generated pNA was diazotized by adding the following solutions sequentially: 975 microliter 0.04% sodium nitrite, 975 microliter 0.3% ammonium sulfamate and 975 microliter 0.07% N-(l-naphthyl)-ethylenediamine dihydrochloride. Diazotization changed pNA from yellow to pink. Then, absorbance at 545 nm was read, and values were expressed as thrombin units/ml plasma. In the modified PT method, 100 microliter citrated plasma (diluted to 20-fold), 90 microliter 1 mM S-2238 and 200 microliter tissue thromboplastin-C solution were mixed and processed as above. Correlations of the present modified APTT and APTT methods, and of modified PT and PT methods were significant (r = 0.426, p less than 0.01 and r = 0.561, p less than 0.01, respectively).

Aniline Compounds↗