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Biomedical subjects

K Akasaka

Publications and source records attributed to K Akasaka.

At least 127 records · Page 7Linked to original sources
PubMed1992

[Therapeutic effects of cefclidin against severe infections in patients with hematopoietic disorders. Hanshin Infection Study Group].

One hundred thirty-eight patients with severe infections associated with hematopoietic disorders were treated with cefclidin (CFCL), and the efficacy and the safety of the drug were evaluated. The results obtained are summarized below. 1. Of the 126 patients in whom the efficacies were evaluable, 22 (17.5%) responded markedly well and 48 (38.1%) moderately, and the overall efficacy rate was 55.6%. 2. Efficacy rates for different infections were: 20.0% in septicemia, 61.2% in suspected septicemia, 46.7% in respiratory tract infection and 25.0% in others. 3. Significantly different efficacy ratings were observed between a group of patients with neutrophil counts of less than 100/mm3 and that with neutrophil counts of higher than 501/mm3. 4. Out of 138 patients in whom the safety was evaluable, side effects were observed in 5 patients (3.6%) and abnormal laboratory test values in 9 (6.5%). None was serious, however.

Adolescent↗
PubMed1992

[Late phase II study of MST-16 (sobuzoxane) efficacy for malignant lymphoma].

A late phase II study with MST-16 for malignant lymphoma was performed with the collaboration of 11 institutions belonging to the Hanshin Hematological Disease Treatment Research Group. Out of a total 40 patients entered into the study, 37 cases (33 of NHL and 4 HD) were evaluated for efficacy and 27 cases for side effects. The response rate was 29.7% (2 cases of CR and 9 PR). The factors affecting response rate were histological classification, phenotype of tumor cell surface and stage of disease. Bone marrow suppression and G-I disorders were the main toxicities observed, but they disappeared by the cessation of MST-16 treatment.

Adult↗
PubMed1991

Mobility of the terminal regions of flagellin in solution.

The mobility of the disordered terminal regions of flagellin was examined in detail based on 1H NMR chemical shifts and spin-lattice relaxation times in the rotating frame. Proteolytic fragments of flagellin with terminal deletions of different sizes were used to compare the dynamical properties of various N- and C-terminal segments. We found that dynamic properties of different terminal segments were similar to each other and were close to those of the heat-denatured state of flagellin. The main chain of these terminal segments undergoes rapid motions with effective correlation times of 1.3-4.1 x 10(-9) s. The terminal regions contain no large segments with well-defined structure. However, comparison with the random-coiled state of poly-L-lysine suggests significant structural constraints in the terminal regions (as well as in the heat-denatured flagellin) which may reflect the existence of some highly fluctuating secondary structure, as suggested by earlier CD studies.

Amino Acid Sequence↗
PubMed1991

Structure of the active 27-residue fragment of human calpastatin.

A synthetic 27-residue peptide corresponding to exon 1B of the endogenous inhibitor calpastatin contains a well-conserved region and has an ability to inhibit the cysteine endopeptidase calpain specifically. We examined the solution structure of this peptide in DMSO-d6 by two-dimensional 1H NMR spectroscopy. Although regular secondary structures such as alpha-helix and beta-sheet were not found, the region from Ile18 to Arg23 formed a well-defined structure with a type I beta-turn. This region coincided well with the highly conserved region of calpastatin. The result strongly suggests that this turn structure is essential for the inhibitory activity of calpastatin.

Amino Acid Sequence↗
PubMed1991

Cold denaturation and heat denaturation of Streptomyces subtilisin inhibitor. 1. CD and DSC studies.

Cold denaturation and heat denaturation of the protein Streptomyces subtilisin inhibitor (SSI) were studied in the pH range 1.84-3.21 and in the temperature range -3-70 degrees C by circular dichroism and scanning microcalorimetry. The native structure of the protein was apparently most stabilized at about 20 degrees C and was denatured upon heating and cooling from this temperature. Each denaturation was reversible and cooperative, proceeding in two-state transitions, that is, from the native state to the cold-denatured state or from the native state to the heat-denatured state. The two denatured states, however, were not perfect random-coiled structures, and they differed from each other, indicating that there exist three states in this temperature range, i.e., cold denatured, native, and heat denatured. The difference between the cold and heat denaturations was indicated first by circular dichroism. The isodichroic point for the transition from the native state to the cold-denatured state was different from that from the native state to the heat-denatured state in the pH range between 3.21 and 2.45. Moreover, molar ellipticity for the cold-denatured state was different from that of the heat-denatured state, and the transition from the former to the latter was observed at pH values below 2. Values of van't Hoff enthalpies from the native state to the heat-denatured state at pH values between 3.21 and 2.45 were obtained by curve fitting of the CD data, and delta Cp = 1.82 (+/- 0.11) [kcal/(mol.K)] was obtained from the linear plot of the enthalpies against temperature. The parameters obtained from the heat denaturation studies gave curves for delta G zero which were not in agreement with the experimental data in the cold denaturation region when extrapolated to the low temperature. Moreover, the value of the apparent delta Cp for the cold denaturation in the pH range 3.03-2.45 was estimated to be different from that for the heat denaturation, indicating that the mechanism of the cold denaturation of SSI is different from a simple cold denaturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1991

Cold denaturation and heat denaturation of Streptomyces subtilisin inhibitor. 2. 1H NMR studies.

Structural transitions of the protein Streptomyces subtilisin inhibitor (SSI) from the native state to the cold-denatured and heat-denatured states were studied by 1H NMR spectroscopy in the temperature range from -10 to 60 degrees C in the acidic pH range. Assignments of some of the 1H NMR signals of SSI in the cold-denatured and heat-denatured states were performed by a combined use of selective deuteration and site-directed mutagenesis. Throughout the pH range from 2.1 to 3.1, both transitions were cooperative and basically only three distinct spectra corresponding to structures in the cold-denatured, native, and heat-denatured states were detected. In the cold-denatured state, the side-chain signals of Met73, His106, at least one Val, and two Leu were observed at distinctly shifted positions from those for a random-coiled structure, suggesting the formation of a tertiary structure, while those of Met70, His43, and Ala2 were observed at positions for a random-coiled structure. This tertiary structure in the cold-denatured state is entirely different from that in the native state, as some amino acid residues exposed to the solvent in the native state (e.g., Met73, His106) are buried while those sequestered in the native state (e.g., His43) are exposed. In the heat-denatured state, however, most 1H NMR signals were observed at random-coiled positions, indicating that there is much less tertiary structure in the heat-denatured state than in the cold-denatured state. At pH values below 2.09, a structural transition was observed from the cold-denatured state to the heat-denatured state without passing through the native state.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Mechanisms of temporary inhibition in Streptomyces subtilisin inhibitor induced by an amino acid substitution, tryptophan 86 replaced by histidine.

Just one amino acid substitution (Trp86 replaced by His), which is more than 30 A away from the reactive site, changed the inhibitor, Streptomyces subtilisin inhibitor (SSI), into a temporary inhibitor without a change in the inhibition constant. When the inhibitor was in excess of subtilisin BPN', the wild-type SSI was stable under protease attack, while the mutant inhibitor was hydrolyzed to peptide fragments in an all-or-none manner. The mechanism of this temporary inhibition induced by the amino acid substitution was studied on the basis of structural, thermodynamic, and kinetic data obtained by a combined use of NMR, hydrogen-deuterium exchange, differential scanning calorimetry, and gel filtration HPLC. The mutation did not induce major structural changes, and in particular, the structure of the enzyme-binding region was virtually unaffected. The denaturation temperature of SSI, however, was decreased by 10 deg upon mutation, although it still remained a thermostable protein with a denaturation temperature of 73 degrees C. Furthermore, the activation enthalpy for denaturation was reduced dramatically, to half that of the wild type. When the mutated SSI is present in excess of the enzyme, the proteolysis followed first-order reaction kinetics with respect to the total concentration of the mutated SSI molecules present. From these combined results, we conclude that the proteolysis proceeds not through the native form of the inhibitor in the inhibitor-enzyme complex but through the denatured (unfolded) form of the inhibitor whose fraction is increased by the mutation. This conclusion states that the necessary condition for being a serine protease inhibitor lies not only in the design of the reactive site structure that is highly resistant to protease attack but also in the suppression of such structural fluctuation that brings about cooperative denaturation. In contrast, when the protease existed in excess of the mutated inhibitor, the proteolysis reaction was accelerated by more than 2 orders of magnitude. Furthermore, the reaction occurred even in the wild-type SSI at a comparable rate as in the mutated protein. This indicates that in the enzyme excess case another, more efficient digestion mechanism involving fluctuation within the native manifold of the inhibitor dominates.

Bacterial Proteins↗
PubMed1991

Temperature-jump NMR study of protein folding: ribonuclease A at low pH.

The kinetic process of folding of bovine pancreatic ribonuclease A in a 2H2O environment at pH 1.2 was examined by a recently developed temperature-jump NMR method (Akasaka et al., (1990) Rev. Sci. Instrum. 61, 66-68). Upon temperature-jump down from 45 degrees C to 29 degrees C, which was attained within 6 s, the proton NMR spectral changes were followed consecutively in time intervals of seconds. There was a rapid spectral change, which was finished within the jump period, followed by a much slower process which lasted for a minute or longer. Rates of the slower process were measured at different positions of the polypeptide chain as intensity changes of individual His and Tyr proton signals of the folded conformer and as intensity changes of aliphatic and His protons of the unfolded conformer. Most of these rates coincided with each other within experimental error with an average value of 2.8 x 10(-2) s-1. The result gave clear experimental evidence that the slow folding of RNase A at low pH is a cooperative process involving most regions of the molecule, not only thermodynamically, but kinetically as well.

Animals↗
PubMed1991

A novel peptide isolated from the leaves of Gymnema sylvestre--I. Characterization and its suppressive effect on the neural responses to sweet taste stimuli in the rat.

1. A new substance that suppressed selectively the neural responses of the rat to sweet taste stimuli was isolated from the leaves of Gymnema sylvestre. 2. The substance was proved to be a peptide consisting of 35 amino acids and having a molecular weight of about 4,000. 3. The inhibitory effect on the sweet responses appeared after treating the tongue surface with the peptide at a concentration of more than 1 x 10(-6) M.

Animals↗
PubMed1991

[Clinical and cytological features of acute myelogenous leukemia with 8; 21 chromosome translocation].

Eight cases of acute myelogenous leukemia with (8; 21) translocation were reported. As recently reported, they showed following features: M2 morphology in FAB classification (all 8 patients), abnormal granulocyte maturation, i.e. large granules and pseudo Pelger-Huet forms (5), Auer rods (8), occasional eosinophilia (2), frequent loss of one sex chromosome (5), the low neutrophil alkaline phosphatase activity (5), and tumor formation (one). Both CD13 and CD33 antigens were expressed on smaller number of leukemic cells than the other AML (M2) cells, whereas CD34 and HLA-DR antigens were expressed on higher number of cells. Interestingly CD19 antigen was detected on a small to large population of tumor cells from four out of six patients. Despite the high remission rate, many of them relapsed within one year. More intensive postinduction and maintenance therapy should be considered for those patients.

Adolescent↗
PubMed1990

Termini of Salmonella flagellin are disordered and become organized upon polymerization into flagellar filament.

The terminal regions of Salmonella flagellin are essential for polymerization to form the flagellar filament. It has recently been suggested, on the basis of results from circular dichroism spectroscopy and scanning calorimetry, that these regions are disordered in solution. We report here direct evidence for disorder and mobility in the terminal regions of flagellin using 400 MHz proton nuclear magnetic resonance (n.m.r.) spectroscopy. Comparison of the n.m.r. spectra of monomeric and polymeric flagellin shows that the terminal regions become organized when polymerized to form the filament.

Bacterial Proteins↗
PubMed1990

[Clinical evaluation of combination therapy with aspoxicillin and ceftazidime for severe infections complicating hematological disorders].

Clinical effects of a combination therapy using aspoxicillin (ASPC) and ceftazidime (CAZ) were investigated in 88 patients with severe infections which were complicating hematological disorders. ASPC and CAZ were administered intravenously at daily doses of 8 g and 4 to 6 g, respectively, in 2 to 4 divided doses for at least 3 days. The treatment was markedly effective in 20 cases; effective in 31; fairly effective in 4; and ineffective in 33 cases. Seventy-seven patients with whom detailed data were obtained showed an efficacy rate of 63.6%. Bacteria were detected in 9 patients, from whom 10 strains were isolated. The results of bacteriological effects were: 3 strains disappeared, 1 decreased, 3 unchanged, and 3 unclear. The bacteriological eradication rate was 42.9%. Of the detected 10 strains, 3 were identified as Pseudomonas aeruginosa, with 2 of the 3 strains eradicated and 1 decreased. An evaluation of the relationship between clinical efficacies and neutrophil counts before and after the ASPC-CAZ combination therapy showed that the patients with 500/mm3 or higher neutrophil counts before the therapy or those with increased neutrophils after the therapy tended to be more responsive to the therapy. Side effects were observed in 4 patients, but all of them disappeared upon discontinuation of the therapy. The combination therapy with ASPC and CAZ appears to be useful for the treatment of severe infections complicating hematological disorders.

Adolescent↗
PubMed1989

Structure of sea-urchin arylsulfatase gene.

The gene encoding arylsulfatase (Ars; EC 3.1.6.1) as well as two Ars pseudogenes were isolated from sea urchin genomic libraries. The Ars gene was 20-kbp long and contained six exons interrupted by five introns. Four polypyrimidine repetitive sequences were dispersed in its upstream-flanking region. Comparison of the amino acid sequence of sea-urchin arylsulfatase with those of human sterol sulfatase, human arylsulfatase A and bacterial arylsulfatase revealed that they have two similar sequences in common. The position of the transcription-start site of the Ars gene was determined to be approximately 40-bp upstream from the 5' end of the protein-coding region, and the nucleotide sequence of the 5'-flanking region was determined up to 3.3 kbp upstream from the transcription start point. Putative TATAA box and CCAAT consensus sequences were located at positions -28 and -82, respectively. A highly conserved hexamer motif, CTCTTT, localized near the transcription-start site of the sea-urchin Ars gene, was also detected in similar regions of other sea urchin genes such as CyIIIa, Spec 1, Spec 2a, Spec 2c, Spec 2d, and SM50, but not in the histone genes.

Amino Acid Sequence↗
PubMed1989

[Therapeutic effects of imipenem/cilastatin sodium against severe infections in patients with hematopoietic disorders. Hanshin Infection Study Group].

One hundred ninety-eight patients with severe infections associated with hematopoietic disorders were treated with imipenem/cilastatin sodium (IPM/CS), and the efficacy and safety of the drug were evaluated. The results obtained are summarized below. 1. Out of 182 patients in whom efficacies are evaluable, responses were excellent in 50 patients, good in 52, fair in 21 and poor in 59, and the efficacy rating was 56.0%. 2. The efficacy rating in 87 patients who had failed to respond to prior treatment with other antibiotics was 58.6%. 3. There were significant differences in efficacy ratings when patients were grouped according to differences the number of neutrophils after treatment, less than 100, 101 approximately 500 and over 501/mm3. 4. The eradication rate in 38 patients from whom causative organisms were isolated was 75.8%. 5. Out of 197 patients in whom the safety was evaluable, side effects were observed in 19 patients (9.6%) and abnormal laboratory test values in 15 (7.6%).

Adolescent↗
PubMed1989

[Factor V inhibitor with double cancer].

A 84-year-old man was admitted with palpitation, edema of legs and anemia during a long course of diabetes mellitus, prostatic hypertrophy and prostatic cancer. He revealed purpura on the hands and massive microhematuria. He had received antibiotic therapy for a urinary tract infection for a period of time, but he had no history of hemorrhagic tendency or blood transfusion. Coagulation studies showed the prolongation of whole blood clotting time and PT (prothrombin time). Activity of factor V was 14% of that normal control plasma. The titer of factor V inhibitor was 4.9 Bethesda units/ml. The inhibitor of the patient was supposed to belong to IgA and IgG judging from inhibitor neutralization test. PT was improved after discontinuance of administration of antibiotics and administration of azathioprine. Moreover, even after administration of prednisolone with antibiotics, PT and activity of factor V recovered to normal range. He died from respiratory failure. Autopsy revealed double cancer of prostate and descending colon. The appearance of factor V inhibitor was likely caused by antibiotics, double cancer, and age-related immune disorders.

Aged↗
PubMed1988

cDNA cloning, nucleotide sequence and expression of the gene for arylsulfatase in the sea urchin (Hemicentrotus pulcherrimus) embryo.

Arylsulfatase is known to be synthesized in large amounts at the early gastrula stage of sea urchin development. We determined the amino acid sequence of a portion of the purified sea urchin embryonic arylsulfatase, and then isolated a cDNA clone for arylsulfatase by screening a sea urchin plutei lambda gt10 cDNA library with an oligodeoxynucleotide probe synthesized according to the determined amino acid sequence. The longest cDNA clones were selected and the nucleotide sequence determined. The cDNA is 2422 nucleotides long and encodes 551 amino acids. The deduced amino acid sequence has not sequence similarity with any of the peptides registered in NBRF peptide databank. Northern blot analysis revealed that the arylsulfatase cDNA hybridizes to a 2.9-kb mRNA. This mRNA exists in the unfertilized egg in small amounts, but markedly increases after the blastula stage preceding the increase of the arylsulfatase activity.

Amino Acid Sequence↗
PubMed1988

Internal motion of a tryptophan residue in Streptomyces subtilisin inhibitor: deuterium nuclear magnetic resonance in solution.

Deuterium NMR spectroscopy was used to study internal motions of a deuterium-labeled single tryptophan (Trp) residue (per subunit) of Streptomyces subtilisin inhibitor (SSI) in solution. The free inhibitor with the five ring protons of the Trp replaced with deuterons showed a narrow resonance component (56 Hz) of about one-quarter of the total intensity, in addition to the broad resonance component (about 600 Hz) at 25 degrees C, showing that it exits in an equilibrium mixture of two conformers, in one of which the tryptophan side chain is highly mobile. In analogy to the two structures of SSI found in the crystal, these two conformers were attributed to the one in which the contact between the alpha-lobe and the beta-lobe of the subunit is tight and the other in which the same contact is loose. When SSI forms a complex with subtilisin BPN', the broad component becomes invisibly broad, but the narrow component increases with even further narrowing, suggesting that the binding to the enzyme favors the "loose" conformer over the "tight" conformer.

Bacterial Proteins↗