Biomedical subjects

K Maki

Publications and source records attributed to K Maki.

At least 19 recordsLinked to original sources

PubMed2000

Quasiparticle bound states around impurities in d(x(2)-y(2))-wave superconductors

Zn and Ni impurities in the hole-doped high-temperature superconductors are known to have strong effects on thermodynamic and transport properties. A recent scanning tunneling microscope study of Zn-doped Bi2212 [S. H. Pan et al., Nature (London) 403, 746 (2000)] has provided high-resolution images of the local density of states around nonmagnetic impurities in d(x(2)-y(2))-wave superconductors. These pictures contain detailed information about the spinor wave functions u(r) and v(r) of bound states with energy E0 approximately Delta/30, centered at the Zn sites. We show that this type of wave function follows from the solutions of the Bogoliubov-de Gennes equations for d(x(2)-y(2))-wave superconductors.

Journal Article↗

PubMed2000

Acetylation of GATA-3 affects T-cell survival and homing to secondary lymphoid organs.

Acetylation of a transcription factor has recently been shown to play a significant role in gene regulation. Here we show that GATA-3 is acetylated in T cells and that a mutation introduced into amino acids 305-307 (KRR-GATA3) creates local hypoacetylation in GATA-3. Remarkably, KRR-GATA3 possesses the most potent suppressive effect when compared with other mutants that are disrupted in putative acetylation targets. Expressing this mutant in peripheral T cells results in defective T-cell homing to systemic lymphnodes, and prolonged T-cell survival after activation. These findings have significant implications in that the acetylation state of GATA-3 affects its physiological function in the immune system and, more importantly, provides evidence for the novel role of GATA-3 in T-cell survival and homing to secondary lymphoid organs.

Acetylation↗

PubMed2000

Immunoglobulin beta signaling regulates locus accessibility for ordered immunoglobulin gene rearrangements.

The antigen receptor gene rearrangement at a given locus is tightly regulated with respect to cell lineage and developmental stage by an ill-defined mechanism. To study the possible role of precursor B cell antigen receptor (pre-BCR) signaling in the regulation of the ordered immunoglobulin (Ig) gene rearrangement during B cell differentiation, a newly developed system using mu heavy (H) chain membrane exon (microm)-deficient mice was employed. In this system, the antibody-mediated cross-linking of Igbeta on developmentally arrested progenitor B (pro-B) cells mimicked pre-BCR signaling to induce early B cell differentiation in vivo. Analyses with ligation-mediated polymerase chain reaction revealed that the Igbeta cross-linking induced the redirection of Ig gene rearrangements, namely, the suppression of ongoing rearrangements at the H chain locus and the activation of rearrangements at the light (L) chain locus. Upon the cross-linking, the kappaL chain germline transcription was found to be upregulated whereas the V(H) germline transcription was promptly downregulated. Notably, this alteration of the accessibility at the H and L chain loci was detected even before the induction of cellular differentiation became detectable by the change of surface phenotype. Thus, the pre-BCR signaling through Igbeta appears to regulate the ordered Ig gene rearrangement by altering the Ig locus accessibility.

Animals↗

PubMed2000

Systematic circular permutation of an entire protein reveals essential folding elements.

The importance of chain connectivity in determining protein function and stability can be examined by breaking the peptide backbone using a technique such as circular permutation. Cleavage at certain positions results in a complete loss of the ability of the protein to fold. When such cleavage sites occur sequentially in the primary structure, we call the region a 'folding element', a new concept that could assist in our understanding of the protein folding problem. The folding elements of dihydrofolate reductase have been assigned by conducting a systematic circular permutation analysis in which the peptide backbone was sequentially broken between every pair of residues in the protein. The positions of folding elements do not appear to correspond to secondary structure motifs, substrate or coenzyme binding sites, or accessible surface area. However, almost all of the amino acid residues known to be involved in early folding events are located within the folding elements.

Binding Sites↗

PubMed2000

In vitro activities of a new lipopeptide antifungal agent, FK463, against a variety of clinically important fungi.

The in vitro antifungal activity and spectrum of FK463 were compared with those of amphotericin B, fluconazole, and itraconazole by using a broth microdilution method specified by National Committee for Clinical Laboratory Standards document M27-A (National Committee for Clinical Laboratory Standards, Wayne, Pa., 1997). FK463 exhibited broad-spectrum activity against clinically important pathogens including Candida species (MIC range, <==0.0039 to 2 microg/ml) and Aspergillus species (MIC range, <==0.0039 to 0.0313 microg/ml), and its MICs for such fungi were lower than those of the other antifungal agents tested. FK463 was also potently active against azole-resistant Candida albicans as well as azole-susceptible strains, and there was no cross-resistance with azoles. FK463 showed fungicidal activity against C. albicans, i.e., a 99% reduction in viability after a 24-h exposure at concentrations above 0.0156 microg/ml. The minimum fungicidal concentration (MFC) assays indicated that FK463 was fungicidal against most isolates of Candida species. In contrast, the MFCs of FK463 for A. fumigatus isolates were much higher than the MICs, indicating that its action is fungistatic against this species. FK463 had no activity against Cryptococcus neoformans, Trichosporon species, or Fusarium solani. Neither the test medium (kind and pH) nor the inoculum size greatly affected the MICs of FK463, while the addition of 4% human serum albumin increased the MICs for Candida species and A. fumigatus more than 32 times. Results from preclinical in vitro evaluations performed thus far indicate that FK463 should be a potent parenteral antifungal agent.

Antifungal Agents↗

PubMed2000

Efficacy of FK463, a new lipopeptide antifungal agent, in mouse models of disseminated candidiasis and aspergillosis.

The efficacy of intravenous injection of FK463, a novel water-soluble lipopeptide, was evaluated in mouse models of disseminated candidiasis and aspergillosis and was compared with those of fluconazole (FLCZ) and amphotericin B (AMPH-B). In the candidiasis model, FK463 significantly prolonged the survival of intravenously infected mice at doses of 0.125 mg/kg of body weight or higher. In disseminated candidiasis caused by Candida species, including FLCZ-resistant Candida albicans, FK463 exhibited an efficacy 1.4 to 18 times inferior to that of AMPH-B, with 50% effective doses (ED(50)s) ranging from 0.21 to 1.00 mg/kg and 0.06 to 0.26 mg/kg, respectively, and was much more active than FLCZ. The protective effect of FK463 was not obviously influenced by the fungal inoculum size, the starting time of the treatment, or the immunosuppressed status of the host. The reduction in efficacy was less than that observed with FLCZ or AMPH-B. The efficacy of FK463 was also evaluated in the disseminated candidiasis target organ assay and was compared with those of FLCZ and AMPH-B. Efficacies were evaluated on the basis of a comparison between the mean log(10) CFU in kidneys in the groups treated with antifungal agents and that in control group. A single dose of FK463 at 0.5 mg/kg or higher significantly reduced the viable counts in kidneys compared with the numbers of yeast cells before treatment, and its efficacy was comparable to that of AMPH-B, while FLCZ at 4 mg/kg showed only a suppressive effect on the growth of C. albicans in the kidneys. In the disseminated aspergillosis model, FK463 given at doses of 0.5 mg/kg or higher significantly prolonged the survival of mice infected intravenously with Aspergillus fumigatus conidia. The efficacy of FK463 was about 2 times inferior to that of AMPH-B, with ED(50)s ranging from 0.25 to 0.50 mg/kg and 0.11 to 0.29 mg/kg, respectively. These results indicate that FK463 may be a potent parenterally administered therapeutic agent for disseminated candidiasis and aspergillosis.

Animals↗

PubMed2000

Changes in cortical bone mineralization in the developing mandible: a three-dimensional quantitative computed tomography study.

Quantitative computed tomography (QCT) was completed in 34 subjects between the ages of 9 and 33 years with symmetrical mandibles in order to investigate the three-dimensional cortical bone mineral density (BMD) distribution in the mandible. The number and distribution of the pixels were determined at three levels: (1) representing the entire mandibular bone; (2) the cortical bone at 60% above the baseline defined as the segmentation level (around 1050 mg/cm3) and representative of only cortical bone; and (3) the highest mineralized cortical bone (>1250 mg/cm3). The geometrical distribution of the highest mineralized areas was evaluated by three-dimensional reconstruction of the images. The total number of pixels for the entire mandible increased significantly at each time point represented at four increasing ages groups (9-11 years of age, 12-14 years of age, 15-17 years of age, and >18 years of age). The male and female subjects had a similar total number of pixels for the entire mandible before the age of 11, but the male subjects showed a significantly larger total number of mandibular pixels after that age. Comparison of the number of pixels for pure cortical bone (60% segmentation level) and the highest mineralized cortical bone indicated a significant increase with maturation with the greatest change occurring between the 13-year and 16-year age groups. However, the ratio of cortical bone/total bone increased at a more rapid rate in the male subjects and reached a plateau by the 16-year age group, showing distinct differences in mineralization of the mandible between the sexes.

Adolescent↗

PubMed1999

Transcriptional inhibition of p53 by the MLL/MEN chimeric protein found in myeloid leukemia.

The t(11;19)(q23;p13.1) translocation is frequently found in adult myeloid leukemia. In the MLL/MEN fusion protein generated by this translocation, most of the coding region of the MEN protein, an RNA polymerase II elongation factor, is fused to the N-terminal third of the MLL protein, a possible transcriptional regulator. However, the molecular mechanism of leukemogenesis by the fusion protein remains unclear. We investigated the effects of the fusion protein on p53 function using luciferase assays. Overexpression of the fusion protein suppressed the transactivation ability of p53. This negative effect of the fusion protein on p53 function was dependent on the region derived from MEN. Moreover, p53 coimmunoprecipitated with MLL/MEN as well as MEN, suggesting that the fusion protein binds to p53 through the MEN region. We found that MEN binding to p53 was mediated by its N-terminal region and repression of p53 transcriptional activity was mediated by its C-terminal region. We also found that these two functional regions were essential for the transformation of Rat1 cells mediated by MEN. Although we could not demonstrate a functional difference between MLL/MEN and MEN in this study, these data suggest that the MLL/MEN chimeric transcriptional regulator may exert its oncogenic activity by inhibiting the function of the p53 tumor-suppressor protein by binding to it. Our findings provide a novel insight into the leukemogenic mechanism exerted by the t(11;19)(q23;p13.1) translocation.

Adult↗

PubMed1999

Effects of proline mutations on the folding of staphylococcal nuclease.

Effects of proline isomerizations on the equilibrium unfolding and kinetic refolding of staphylococcal nuclease were studied by circular dichroism in the peptide region (225 nm) and fluorescence spectra of a tryptophan residue. For this purpose, four single mutants (P11A, P31A, P42A, and P56A) and four multiple mutants (P11A/P47T/P117G, P11A/P31A/P47T/P117G, P11A/P31A/P42A/P47T/P117G, and P11A/P31A/P42A/P47T/P56A/P117G) were constructed. These mutants, together with the single and double mutants for Pro47 and Pro117 constructed in our previous study, cover all six proline sites of the nuclease. The P11A, P31A, and P42A mutations did not change the stability of the protein remarkably, while the P56A mutation increased protein stability to a small extent by 0.5 kcal/mol. The refolding kinetics of the protein were, however, affected remarkably by three of the mutations, namely, P11A, P31A, and P56A. Most notably, the amplitude of the slow phase of the triphasic refolding kinetics of the nuclease observed by stopped-flow circular dichroism decreased by increasing the number of the proline mutations; the slow phase disappeared completely in the proline-free mutant (P11A/P31A/P42A/P47T/P56A/P117G). The kinetic refolding reactions of the wild-type protein assessed in the presence of Escherichia coli cyclophilin A showed that the slow phase was accelerated by cyclophilin, indicating that the slow phase was rate-limited by cis-trans isomerization of the proline residues. Although the fast and middle phases of the refolding kinetics were not affected by cyclophilin, the amplitude of the middle phase decreased when the number of the proline mutations increased; the percent amplitudes for the wild-type protein and the proline-free mutants were 43 and 13%, respectively. In addition to these three phases detected with stopped-flow circular dichroism, a very fast phase of refolding was observed with stopped-flow fluorescence, which had a shorter dead time (3.6 ms) than the stopped-flow circular dichroism. The following conclusions were drawn. (1) The effects of the P11A, P31A, and P56A mutations on the refolding kinetics indicate that the isomerizations of the three proline residues are rate-limiting, suggesting that the structures around these residues (Pro11, Pro31, and Pro56) may be organized at an early stage of refolding. (2) The fast phase corresponds to the refolding of the native proline isomer, and the middle phase whose amplitude has decreased when the number of proline mutations was increased may correspond to the slow refolding of non-native proline isomers. The occurrence of the fast- and slow-refolding reactions together with the slow phase rate-limited by the proline isomerization suggests that there are parallel folding pathways for the native and non-native proline isomers. (3) The middle phase did not completely disappear in the proline-free mutant. This suggests that the slow-folding isomer is produced not only by the proline isomerizations but also by another conformational event that is not related to the prolines. (4) The very fast phase detected with the fluorescent measurements suggests that there is an intermediate at a very early stage of kinetic refolding.

Amino Acid Substitution↗

PubMed1999

Neonatal hyperbilirubinemia and a common mutation of the bilirubin uridine diphosphate-glucuronosyltransferase gene in Japanese.

Neonatal hyperbilirubinemia, which is prevalent among Asian peoples, has been considered as a physiological phenomenon, and its metabolic basis has not been clearly explained. Gilbert syndrome is a common inherited disease of unconjugated hyperbilirubinemia due to decreased bilirubin uridine diphosphate-glucuronosyltransferase (B-UGT), and its role in neonatal jaundice has recently been considered. We have previously reported that the Gly71Arg mutation of the B-UGT gene associated with Gilbert syndrome is prevalent in Japanese, Korean, and Chinese populations and was more frequently detected in neonates with severe hyperbilirubinemia than in control subjects. We have studied 159 Japanese full-term neonates, evaluating the relationship between the B-UGT genotype and the severity of jaundice, as assessed with a transcutaneous bilirubinometer. The gene frequency of the Gly71Arg mutation in these neonates was 0.19, and neonates carrying the Gly71Arg mutation had significantly increased bilirubin levels on days 2-4, manifested in a gene dose-dependent manner. The frequency of the Gly71Arg mutation was 0.47 in the neonates who required phototherapy (i.e., those with more severe hyperbilirubinemia), significantly higher than 0.16 in the neonates who did not require the therapy. The gene frequency of the TA repeat promoter polymorphism, the (TA)7 mutation, was 0.07, and neonates carrying this mutation did not have an increase in bilirubin. These results suggested that the Gly71Arg mutation contributes to the high incidence of neonatal hyperbilirubinemia in Japanese.

Base Sequence↗

PubMed1999

Induction of germline transcription in the TCRgamma locus by Stat5: implications for accessibility control by the IL-7 receptor.

IL-7 receptor (IL-7R) plays critical roles in lymphocyte development by promoting survival and proliferation and by inducing V(D)J recombination in TCR and Ig loci. Here, we demonstrate that IL-7R-activated Stat5 binds to consensus motifs in the 5' regions of Jgamma segments and induces germline transcripts. We also show that a constitutively active form of Stat5 restores V-J recombination of TCRgamma genes and partially rescues T cell development from IL-7R(-/-) T cell precursors, especially in favor of gammadelta T cells. Therefore, this study reveals a potential role of Stat5 in T cell development and also implies that IL-7R may control the accessibility of the TCRgamma locus through Stat5-induced germline transcription.

Animals↗

PubMed1999

IL-7 receptor alpha+ CD3(-) cells in the embryonic intestine induces the organizing center of Peyer's patches.

Peyer's patch (PP) organogenesis proceeds through three histologically distinct steps: formation of organizing centers expressing VCAM-1 and ICAM-1 in segregated regions of the intestine at 15.5 days post-coitus (d.p.c.) (step I), accumulation of blood cells expressing different sets of surface markers to this region at 16.5-17.0 d.p.c. (step II), and entry of CD3+ and B220+ lymphocytes just before birth (step III). PP formation of both Il7ra-/- and Lta-/- mice is impaired from step I, suggesting involvement of the two molecules at the same timing in PP organogenesis. Expression of lymphotoxin (LT) alpha and LTbeta in IL-7 receptor (IL-7R) alpha+ cells in the intestine indicates that defects of Il7ra-/- and Lta-/- mice are due to functional inability of IL-7Ralpha+ cells in the induction of PP anlage. Blocking of IL-7Ralpha function by a single injection of the antagonistic mAb in 15.5 d.p.c. embryos suppressed appearance of VCAM-1(+) spots and expression of LTalpha and LTbeta in the intestine, which eventually resulted in mice without PP but are otherwise normal. Intestinal IL-7Ralpha+ cells are lymphoid in morphology but CD3(-) and functional in both nu/nu and Rag2-/- mice. These results implicate IL-7Ralpha+ CD3(-) cells as the direct inducer of the organizing center of PP.

Animals↗

PubMed1999

Early diagnosis of central nervous system aspergillosis with combination use of cerebral diffusion-weighted echo-planar magnetic resonance image and polymerase chain reaction of cerebrospinal fluid.

We treated a patient diagnosed as central nervous system (CNS) aspergillosis with the combined use of cerebral diffusion-weighted echo-planar magnetic resonance imaging (DWI) and polymerase chain reaction of the cerebrospinal fluid (CSF-PCR). DWI, a cutting-edge imaging modality to reveal the earliest changes of cerebral infarction, detected cerebral fungal embolization when the conventional computed tomographic scan and magnetic resonance imaging failed to reveal it. CSF-PCR demonstrated the presence of Aspergillus-specific DNA in the specimen, when the conventional examination and culture of CSF were nonspecific or negative. These diagnostic methods could be useful in the early diagnosis of CNS aspergillosis.

Aspergillosis↗

PubMed1999

Successful transfer of localized autoimmunity with positively selected CD4+ cells to scid mice lacking functional B cells.

T-cell function of athymic BALB/c-nu/nu (nude) mice can be corrected by implantation of a embryonic rat thymus graft (TG) under the renal capsule (TG nude mice). However, multiple organ-localized autoimmune diseases, such as oophoritis, Sjögren's syndrome like disease and gastritis, develop spontaneously in TG nude mice. Transfer of spleen cells from TG nude mice with such diseases leads to multiple localized autoimmune lesions with appearance of the corresponding autoantibodies in the recipient C.B-17-scid (SCID) mice. In the present study, removal of CD90+ or CD4+, but not CD8+ cells eliminated the transfer activity. Positively selected CD4+ cells proved capable of inducing lesions without the appearance of organ-specific autoantibodies, although the grade of lesions was lower than that in recipient mice that received untreated or CD8-depleted spleen cells. Target organs demonstrating CD4+ cell infiltration, generally expressed major histocompatibility complex (MHC) class II antigen (Ia) on their parenchymal cells. Injection of sera from TG nude mice with autoantibodies to SCID mice did not induce any pathogenic features in the autoantibody-target organs, although deposition of immunoglobulins in the corresponding target organs was observed. In such cases, no Ia antigens were expressed on the parenchymal cells. The data thus indicate that effector CD4+ cells can induce autoimmunity without B-cell help but that cooperation with functional B cells induces more severe tissue damage.

Animals↗

PubMed1999

FK463, a novel water-soluble echinocandin lipopeptide: synthesis and antifungal activity.

Explore the source record for details and available documents.

Antifungal Agents↗

PubMed1998

Impaired anaphylactic responses with intact sensitivity to endotoxin in mice lacking a platelet-activating factor receptor.

Platelet-activating factor (PAF) is a potent phospholipid mediator with diverse biological activities in addition to its well-known ability to stimulate platelet aggregation. Pharmacologic studies had suggested a role for PAF in pregnancy, neuronal cell migration, anaphylaxis, and endotoxic shock. Here we show that disruption of the PAF receptor gene in mice caused a marked reduction in systemic anaphylactic symptoms. Unexpectedly, however, the PAF receptor-deficient mice developed normally, were fertile, and remained sensitive to bacterial endotoxin. These mutant mice clearly show that PAF plays a dominant role in eliciting anaphylaxis, but that it is not essential for reproduction, brain development, or endotoxic shock.

Anaphylaxis↗

PubMed1998

Essential role of IL-7 receptor alpha in the formation of Peyer's patch anlage.

We investigated the role of IL-7 receptor alpha (IL-7Ralpha) signal in the formation of Peyer's patch (PP) anlage. Although pan-lymphopenia is a common phenotype of rag2-/- and il7ralpha-/- mice, a close inspection revealed nodules corresponding to PP in the adult rag2-/- but not in the il7ralpha-/- mouse. In our previous study, three histologically distinct steps in the formation of PP were identified. The first is the appearance of VCAM-1 + spots in the intestine, which probably represents an initial stage of the formation of the PP anlage. Accumulation of cells bearing IL-7Ralpha, CD4 or Ia in this region then follows and eventually entry of mature lymphocytes expressing CD3 or B220 occurs just before birth. Based on this criterion, we next investigated which of these events is defective in mice with severe combined immunodeficiency. Formation of VCAM-1 + spots and cluster formation of IL-7Ralpha+ cells proceed normally in the rag2-/- mouse which completely lacks mature lymphocytes. In contrast, no VCAM-1+ spots were detected in the embryonic nor neonatal il7ralpha-/- mice, suggesting that IL-7Ralpha signal is involved in the early phase of PP anlage formation. The same defect was found in the jak3-/- mouse. In addition to the appearance of VCAM1+ spots, the clustering of IL-7Ralpha+ cells was absent in the jak3-/- mouse, though IL-7Ralpha+ cells are found to scatter over the intestine. These results indicate that IL-7Ralpha is an essential signal for an early step of PP anlage formation, without which the subsequent processes cannot be initiated.

Animals↗

PubMed1998

Plasminogen activator inhibitor-1 promoter 4G/5G genotype is not a risk factor for myocardial infarction in a Japanese population.

There is little question that the blood clotting process is triggered and causes the vascular occlusion associated with myocardial infarction. Although it is less clear what part blood coagulation events might play in the etiology of coronary artery disease, impaired regulation of anticoagulation or fibrinolysis might be involved. Among anticoagulant and fibrinolytic factors, an elevated plasma plasminogen activator inhibitor-1 (PAI-1) concentration has been identified as a risk factor for the development of myocardial infarction. An association between one polymorphism of the PAI-1 promoter (4G/5G single nucleotide deletion/ insertion at position -675) and plasma PAI-1 levels was described in 1995. However, most recent studies seem to point to the lack of such an association. This is the first report on the frequency of this polymorphism in the Japanese population with respect to the risk of myocardial infarction. Sixty-six patients with myocardial infarction and sixty-two healthy control patients were chosen for the analysis of the PAI-1 promoter 4G/5G genotype with polymerase chain reaction-single strand conformation polymorphism. Five myocardial infarction patients and six in the control group were homozygous for the 4G/4G genotype. Twenty-eight and 27 4G/5G and 33 and 29 5G/5G genotypes were found in myocardial infarction and control groups, respectively. The total frequencies of the 4G and 5G alleles were approximately 30% and 70% in both control and myocardial infarction groups. In conclusion, the PAI-1 promoter genotype is not a risk factor for myocardial infarction in the Japanese population. This is in contrast to the first report in Caucasians, suggesting an interaction with other genetic or environmental factors which influences the risk of myocardial infarction.

Aged↗