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Biomedical subjects

I Kato

Publications and source records attributed to I Kato.

At least 145 records · Page 8Linked to original sources
PubMed1998

Cyclic ADP-ribose and inositol 1,4,5-trisphosphate as alternate second messengers for intracellular Ca2+ mobilization in normal and diabetic beta-cells.

Intracellular Ca2+ mobilization occurs in a variety of cellular processes and is mediated by two major systems, the inositol 1,4, 5-trisphosphate (IP3) and cyclic ADP-ribose (cADPR) systems. cADPR has been proposed to be a second messenger for insulin secretion induced by glucose in pancreatic beta-cells (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). Here we show that the cADPR signal system for insulin secretion is replaced by the IP3 system in diabetic beta-cells such as ob/ob mouse islets and RINm5F cells. We measured the cADPR content in these beta-cells by radioimmunoassay and found that the increase of the cADPR content by glucose did not occur in ob/ob mouse islets and RINm5F cells, whereas the increased cADPR level by glucose was observed in normal rat and mouse islets. Microsomes of these diabetic beta-cells released Ca2+ in response to IP3 but not to cADPR. In the diabetic beta-cells, CD38 (ADP-ribosyl cyclase/cADPR hydrolase) and type 2 ryanodine receptor mRNAs were scarcely detected and, in contrast, an increased expression of IP3 receptor mRNAs was observed. The diabetic beta-cells secreted insulin rather by carbamylcholine than by glucose.

ADP-ribosyl Cyclase↗
PubMed1998

A novel derivatization method with 5-bromonicotinic acid N-hydroxysuccinimide for determination of the amino acid sequences of peptides.

We have developed a novel method that effectively identifies the N-terminal product ions produced in the tandem mass spectrometry (MS/MS) analysis of peptides done in conjunction with the specific derivatization of the N-terminal amino group using 5-bromonicotinic acid N-hydroxysuccinimide ester (BrNA-NHS). Electrospray ionization with low-energy collision-induced dissociation (CID) MS/MS clearly differentiated the N-terminal product ions labeled with the 5-bromonicotinyl group from other ions, on the basis of the appearance of CID peaks with a doublet pattern characteristically separated by 2 mass units produced by the equal natural abundances of 79Br and 81Br. The tracing of a series of these bromine-containing product ions allows the easy amino acid sequencing of peptides. Using Gln-Arg-Leu-Gln-Ser-Asn-Gln-Leu-Lys as the test peptide, we found that within 30 minutes at pH 6.5 and 37 degrees C its alpha-amino group was completely acylated with BrNA-NHS (peptide: BrNA-NHS = 1:40; mol/mol). The epsilon-amino group of the C-terminal lysine residue was less likely to be acylated under these conditions, being only partly modified (about 20%). This suggests the possibility of keeping the epsilon-amino group free from acylation. The method was successfully applied to the determination of the amino acid sequences of peptides from porcine kidney aminoacylase I produced by digestion with lysyl endopeptidase and with Staphylococus aureus V8 protease.

Amino Acid Sequence↗
PubMed1998

High-resolution crystals of methionine aminopeptidase from Pyrococcus furiosus obtained by water-mediated transformation.

The monoclinic crystal form of methionine amino-peptidase from Pyrococcus furiosus (MAP-Pfu) has been crystallized from four different conditions. Native crystals belong to space group P2(1) with typical unit-cell dimensions a = 53.4, b = 85.1, c = 72.7 A, beta = 107.7 degrees and diffract to 2.9-4.5 A resolution. However, there is a problem of nonisomorphism among the crystals. Water-mediated transformation to low-humidity form occurs by reduction of the relative humidity of crystal environment to 79%. The unit-cell dimensions of transformed crystals are a = 51.9, b = 83.3, c = 70.3 A, beta = 105.9 degrees, and the calculated solvent content is 3.9% less than in original crystals. Transformation to low-humidity form is accompanied by 1.7 times reduction of overall temperature factors, extension of diffraction resolution up to 1.75 A, without change or reduction of crystal mosaicity, and improvement in stability to X-ray radiation. The water-mediated transformation also appears to relieve the problem of nonisomorphism among the original MAP-Pfu crystals.

Aminopeptidases↗
PubMed1998

Histopathological study of the role of CD4- and CD8-positive T cells on bone resorption induced by Escherichia coli endotoxin.

The purpose of this study was to clarify the involvement of CD4+ and CD8+ T cells on bone resorption induced by Escherichia coli endotoxin. Two kinds of monoclonal antibodies, anti-CD4 and/or anti-CD8, were employed for the depletion of each or both T cell subsets. E. coli endotoxin was injected into mouse mesial gingiva of the first molar of the left mandible every 48 hours for up to 14 days (7 injections). The mice were divided into four groups: CD4-depleted, CD8-depleted, T cell-depleted, and normal. The mice were sacrificed on the day after the 1st, 3rd, 4th, 5th, and 7th injection and alveolar bone was examined histopathologically and histomorphometrically. Bone surface in contact with osteoclasts was defined as the site of active resorption and the ratios of active resorption were compared among the four groups. In addition, sections obtained after the 1st, 4th, and 7th injection were immunohistologically stained in order to confirm the presence or absence of CD4+ or CD8+ T cells. Alveolar bone resorption gradually increased in normal mice as the number of injections increased. In contrast, alveolar bone resorption was significantly weaker in each or both subset-depleted mice. For the duration of the experimental period, the number of CD4+ T cells in CD8-depleted and normal mice significantly increased with increasing bone resorption. Considering the function of CD4+ and CD8+ T cells, these results suggest that each subset preferentially acts as a macrophage activator in the early period of bone resorption induced by E. coli endotoxin.

Animals↗
PubMed1998

Isolation and characterization of the aureobasidin A-resistant gene, aur1R, on Schizosaccharomyces pombe: roles of Aur1p+ in cell morphogenesis.

To study the mechanism of action of the antibiotic aureobasidin A (AbA) on yeasts, we isolated a dominant mutant of Schizosaccharomyces pombe which gave high resistance to AbA. From a genomic library of the mutant, an aur1R mutant gene conferring AbA resistance was isolated. One amino-acid mutation, a substitution of glycine with cysteine at residue 240, was responsible for the acquisition of AbA resistance. The wild-type aur1+ gene was essential for viability, and its over-expression enhanced significant resistance to AbA. The predicted protein of S. pombe aur1R was highly homologous in primary structure and hydropathy profile with that of Saccharomyces cerevisiae AUR1R isolated as an AbA-resistance gene. To analyze a role in cell growth of S. pombe aur1+, temperature-sensitive mutants (aur1ts) were obtained by random mutagenesis procedures using a modified PCR. The aur1ts mutation caused a defect in cell elongation at the non-permissive temperature and finally led to cell death. These results suggest that Aur1p was a target of the antibiotic AbA and was required in the cell elongation of cell-end tips and in the viability of S. pombe.

Amino Acid Sequence↗
PubMed1998

Differential expression of IFN-gamma, IL-4, IL-10, and IL-1beta mRNAs in decalcified tissue sections of mouse lipopolysaccharide-induced periodontitis mandibles assessed by in situ hybridization.

To examine the role of T cell subgroups, Th1 and Th2, in the development of periodontitis, the expression of various cytokines was investigated in a mouse model of alveolar bone resorption using in situ hybridization (ISH) with digoxigenin-labeled oligonucleotides. When mice received repetitive injections with Escherichia coli lipopolysaccharide into the gingiva every 48 h, alveolar bone resorption was detectable after the fourth injection, reaching a maximum after the 13th injection. For the best performance of ISH, we first had to choose a decalcification protocol. Among various decalcification protocols, 10% EDTA (4 degrees C, 5-6 days) was the best for 28S rRNA staining. Positive cells for transcripts of interferon-gamma (Th1 product) were detected after the fourth injection, reaching a maximum after the tenth injection. A similar pattern was obtained for interleukin (IL)-10 mRNA (Th2 product) and IL-1beta, while the positive cell number reached a maximum after the 13th and 10th injections, respectively. The number of IL-4 mRNA (Th2 product)-positive cells remained low till the tenth injection, but increased thereafter. Consequently, we found that the population change from Th1 to Th2 in the inflammation site correlated with the transition from gingivitis to periodontitis, indicating differential roles of T cell subgroups in the development of periodontitis.

Alveolar Bone Loss↗
PubMed1998

Role of medullasin in nifedipine-induced gingival overgrowth in rats.

To clarify the possible pathophysiological role of medullasin, a neutrophil elastase-like proteinase, in nifedipine (NF)-induced gingival overgrowth, a rat model of gingival overgrowth was first established using a diet containing NF. The relation between histopathological changes and the distribution of the proteinase was then investigated. Thirty-two, specific pathogen-free 20 day-old, male, Fisher 344 rats were fed a diet containing NF and killed at 2, 8, 16 and 32 weeks. Control rats (n = 32) were fed the same diet but without the drug. The mandible of each rat was resected and sectioned at 4-microm thickness buccolingually between the first and second molars. Computer image analysis was used to evaluate the extent of overgrowth in the approximal gingiva of each sample. To examine medullasin activity, the mean percentage of medullasin-positive cells per total cells counted in the pocket epithelium and the connective tissue adjacent to the epithelium of approximal gingiva was determined immunohistochemically. The height of the mid-portion and the area in NF-treated group increased significantly with time (with the exception of area at 2 weeks) compared with the corresponding regions in the control group. A marked inflammatory-cell infiltration and elongated rete pegs, especially in the mid-portion of approximal gingiva, were seen in the NF-treated group. The mean percentages of medullasin-positive cells in the NF-treated group at 8, 16 and 32 weeks were significantly higher than those of the control. Although medullasin-positive cells were mainly neutrophils, in several samples of the NF-treated group they were recognized as macrophage-like. These findings suggest that medullasin may be involved in host defence and immunoregulation in a NF-induced rat model of gingival overgrowth.

Animals↗
PubMed1998

Suppressive effects of the oral administration of Lactobacillus casei on type II collagen-induced arthritis in DBA/1 mice.

We investigated the effects of the oral administration of the viable bacterium Lactobacillus casei strain Shirota (LcS), on the development of type II collagen (CII)-induced arthritis (CIA) in DBA/1 mice. Male DBA/1 mice were immunized with an emulsion of 100 microg of CII and complete Freund's adjuvant (CFA). The mice were then given orally a suspension of LcS or distilled water (DW) during the experiment. We observed the development of CIA in the mice, and determined the in vivo and ex vivo CII-specific immune responses in the control and LcS-administered mice. In the control mice, we observed the onset of arthritis at the 27th day after the CII-immunization, and then the severity of CIA developed gradually. In the tested mice, the LcS-treatment reduced the incidence and the development of CIA and the levels of antibody to CII in serum compared with the control mice. The CII-specific IgG2a and IgG2b antibodies in serum were also down regulated in the tested mice. The administration of this bacterium also inhibited delayed-type hypersensitivity response to CII in DBA/1 mice immunized with CII and CFA. The orally administered-LcS suppressed the CII-specific secretion of interferon-gamma from splenocytes ex vivo. From these results, we concluded that the oral administration of LcS was able to modify the humoral and cellular immune responses to CII, and these modifications could result in the reduction of the development of CIA in DBA/1 mice.

Animals↗
PubMed1998

Objective tinnitus caused by an aberrant internal carotid artery.

We report the case of a 29 year-old woman who complained of pulsatile tinnitus and impaired hearing. On otoscopic examination, her right tympanic membrane was observed to be in contact with a mass in the middle ear cavity, with the formation of a meniscus at the point of contact. Using a high-sensitivity microphone inserted into the external auditory canal, we recorded pulsatile tinnitus that was synchronous with the electrocardiogram. Magnetic resonance angiography revealed that the middle ear mass was an aberrant internal carotid artery coursing through the hypotympanum.

Adult↗
PubMed1998

Vertical gaze palsy induced by midbrain lesions and its structural imaging.

We experienced four cases of vertical gaze palsy induced by midbrain lesions. Lesions commonly covered the rostral midbrain, including the rostral interstitial nucleus, dorsomedial to the red nucleus. Two of the four cases resulted from vascular insult, in which a single, unpaired perforator is supposed to innervate the rostral midbrain and medial thalamus bilaterally. One case showed vertical gaze palsy accompanied by bilateral ptosis. The findings agree with recent experimental evidence that a neural substrate in eyelid control lies in the supraoculomotor area immediately dorsal to the oculomotor nucleus. The remaining two cases, a brain hemorrhage and an inflammatory tumor, showed unilateral lesions of the rostral midbrain. In these cases, vertical gazes were not abolished, but were limited in an incomplete way. This may be explained by partial damages of the descending fibers, some of which decussate through the posterior commissure before it reaches the oculomotor nucleus. Thus, clinical signs and symptoms were clarified based on anatomical and physiological points of view.

Adult↗
PubMed1998

Prospective study of factors influencing the onset of natural menopause.

Late or early menopause has been implicated in risk of several chronic diseases in women. To study factors influencing the onset of natural menopause, the authors analyzed the follow-up data of 4694 premenopausal women who enrolled in the New York University Women Study at ages 34-61. In an average of 5.4 years of observation, there were 2035 incidences of menopause, with the median age of 51.3 years. Current smokers experienced menopause 0.75 years earlier than never-smokers. Those who smoked more than 10 cigarettes per day had a 40% increase in risk of earlier menopause. In contrast, women who had three or more children experienced menopause 0.86 years later than nulliparous women, and Jewish women, 0.66 years later than Catholic women. There was also a modest increase in the age at menopause with increasing body mass index. This prospective study provides solid epidemiologic evidence that several factors other than cigarette smoking have impact on the onset of natural menopause.

Adult↗
PubMed1998

Effect of supplementation with chromium picolinate on antibody titers to 5-hydroxymethyl uracil.

Recent in vitro studies have shown that chromium (III) compounds such as chromium picolinate, a popular dietary supplement among people trying to lose weight, produce chromosome damage. We monitored levels of DNA damage in a chromium picolinate supplement trial by measuring antibodies titers to an oxidized DNA base, 5-hydroxymethyl-2'-deoxyuridine (HMdU), by enzyme-linked immunosorbent assays. Ten obese volunteer women completed a 8-week course of 400 micrograms chromium picolinate per day. In either absolute titers or percent of the baseline value, there were no changes in antibody titers at 4 or 8 weeks. The titers were very stable within individuals and those of one individual rarely crossed over others, which was reflected in an intraclass correlation coefficient of 0.99 (95% confidence interval: 0.96-1.00). There were no effects on glucose and lipid metabolism in this period. The results of this trial suggest that chromium (III) picolinate in a dose typically used for nutrient supplementation dose not increase oxidative DNA damage, as measured by anti-HMdU antibody levels.

Analysis of Variance↗
PubMed1998

Identification of the catalytic triad residues of porcine liver acylamino acid-releasing enzyme.

Acylamino acid-releasing enzyme (AARE) [EC 3.4.19.1] is a tetrameric serine protease, which belongs to the oligopeptidase family and specifically removes acetyl amino acids from N-terminally acetylated peptides. By using diisopropyl fluorophosphate, we previously identified one of the residues comprising the catalytic triad of this enzyme as Ser587 [Miyagi, M. et al. (1995) J. Biochem. 118, 771-779]. To elucidate the other two residues forming the catalytic triad of this new serine-type protease, wild-type and four mutant AAREs, in which each candidate residue of the catalytic triad deduced from sequence alignment with other oligopeptidases was substituted by site-directed mutagenesis, were expressed in Escherichia coli as fusion proteins with short peptide chains at both N- and C-termini of a subunit of porcine liver enzyme. All of the recombinant AAREs were estimated to have similar conformational and quaternary structures to the native porcine liver enzyme from their CD spectra and behavior on gel-filtration, but the mutants in which Ala587, Asn675, or Tyr707 was substituted for Ser587, Asp675, or His707, respectively, did not show detectable hydrolytic activity toward acetyl-L-methionyl L-alanine. These facts suggest that Ser587, Asp675, and His707 are essential residues for the AARE activity and comprise the catalytic triad of the enzyme in this order. Thus, AARE has been shown to have a protease-like domain in its C-terminal region, as do other proteins classified as members of the oligopeptidase family.

Amino Acid Sequence↗
PubMed1998

Enhancement of retroviral gene transduction on a dish coated with a cocktail of two different polypeptides: one exhibiting binding activity toward target cells, and the other toward retroviral vectors.

CH-296, a recombinant fragment of human fibronectin (FN) composed of the cell-binding domain (C-domain), heparin-binding domain II (H-domain), and CS1 site, enhances the retrovirus-mediated gene transduction (GT) of hematopoietic stem cells. The RGD sequence in the C-domain is recognized by a variety of cell types through integrin VLA-5, and the LDV sequence in the CS1-site is recognized by integrin VLA-4. Retrovirus particles were also found to bind to the H-domain. Consequently, the CH-296 fragment can enhance GT through binding to both retrovirus particles and target cells that express integrins VLA-5 and/or VLA-4. In this study, we found that the GT efficiency can be maintained at levels comparable to that of CH-271, a FN fragment similar to CH-296 but lacking the CS1 site, when a cocktail of separated functional domains of CH-271 is used. When a dish was coated with a mixture of the C-domain and H-domain (molar ratio, 1:10), the GT efficiency of NIH3T3 cells reached the same level as that of the mother fragment, CH-271. The H-domain in the cocktail can be replaced with other virus-binding components, polylysine, FGF, and the insulin-binding domain of ColV, without the loss of GT efficiency. With other than FN fragments, a cocktail of erythropoietin and polylysine caused higher GT efficiency of Epo-receptor expressing TF-1 cells than in the case of each component alone.

Animals↗
PubMed1998

Pyrrolidone carboxyl peptidase from the hyperthermophilic Archaeon Pyrococcus furiosus: cloning and overexpression in Escherichia coli of the gene, and its application to protein sequence analysis.

A gene for a pyrrolidone carboxyl peptidase (Pcp: EC 3.4.19.3, pyroglutamyl peptidase), which removes amino-terminal pyroglutamyl residues from peptides and proteins, has been cloned from the hyperthermophilic Archaeon Pyrococcus furiosus using its cosmid protein library, sequenced, and expressed in Escherichia coli. The DNA sequence encodes a protein containing 208 amino acid residues with methionine at the N-terminus. Analysis of the recombinant protein expressed in E. coli, including amino acid sequence analysis from the N-terminus by automated Edman degradation and ionspray mass spectrometric analysis of the peptides generated by enzymatic digestions with lysylendopeptidase and Staphylococcus aureus V8 protease, showed its primary structure to be completely identical with that deduced from its cDNA sequence. Comparison of the amino acid sequence of P. furiosus Pcp (P.f.Pcp) with those of bacterial Pcps revealed that a high degree of sequence identity (more than 40%) and conservation of the amino acid residues comprising the catalytic triad, Cys142, His166, and Glu79. On the other hand, a unique short stretch sequence (positions around 175-185) that is absent in bacterial Pcps was found in P.f.Pcp. A similar stretch has also been reported recently in the amino acid sequence of Pcp from the hyperthermophilic Archaeon Thermococcus litoralis [Littlechild et al., in abstracts of the "International Congress on Exthermophiles '98" p. 58 (1998)]. To elucidate their contribution to the hyperthermostability of these enzymes, further structural studies are required.

Amino Acid Sequence↗
PubMed1998

Role of ABC transporters in aureobasidin A resistance.

Aureobasidin A (AbA) has strong antifungal effects arising from an unusual mechanism. We show that AbA interacts with ATP-binding cassette (ABC) transporters in yeast and mammalian cells. We isolated a gene of Saccharomyces cerevisiae that conferred resistance to AbA when the gene was present in multiple copies. The gene was identical to YOR1/YRS1, which confers resistance to oligomycin, reveromycin, and organic anions, none of which have structures similar to that of AbA. We also isolated an aur3R recessive mutant of S. cerevisiae with increased resistance to AbA. Northern hybridization showed that the aur3R mutant expressed not only YOR1 but also the ABC transporter-encoding gene PDR5 at high levels. Genetic studies showed that the aur3R mutant had a mutation in the PDR1 gene, which encodes a transcriptional regulator of PDR5 and YOR1. Analysis of a yor1 disruptant of the aur3/pdr1 mutant showed that both the functional YOR1 gene and the mutation in PDR1 were necessary for AbA resistance. These results suggest that YOR1 is more important than PDR5 for AbA resistance. We found in Candida albicans a novel gene whose sequence was similar to the sequence of YOR1 in S. cerevisiae. The amino acid sequence of the C. albicans YOR1 homolog showed no significant similarity to the sequences of CDR1 and CDR2, which are ABC transporters of C. albicans. Furthermore, AbA inhibited the efflux of the anticancer agent vincristine through P glycoproteins in cancer cells with multidrug resistance.

ATP-Binding Cassette Transporters↗
PubMed1998

High-efficiency gene transfer into normal and adenosine deaminase-deficient T lymphocytes is mediated by transduction on recombinant fibronectin fragments.

Primary human T lymphocytes are powerful targets for genetic modification, although the use of these targets in human gene therapy protocols has been hampered by low levels of transduction. We have shown previously that significant increases in the transduction of hematopoietic stem and progenitor cells with retroviral vectors can be obtained by the colocalization of the retrovirus and target cells on specific fibronectin (FN) adhesion domains (H. Hanenberg, X. L. Xiao, D. Dilloo, K. Hashino, I. Kato, and D. A. Williams, Nat. Med. 2:876-882, 1996). We studied the transfer of genes into primary T lymphocytes by using FN-assisted retroviral gene transfer. Activated T lymphocytes were infected for three consecutive days on the recombinant FN fragment CH-296 with a retroviral vector encoding the murine B7-1 protein. Transduced lymphocytes were analyzed for murine B7-1 expression, and it was found that under optimal conditions, 80 to 89% of the CD3+ lymphocytes were transduced. Gene transfer was predominantly augmented by the interaction between VLA-4 on the T lymphocytes and the FN adhesion site CS-1. Adenosine deaminase (ADA)-deficient primary T lymphocytes transduced on CH-296 with a retrovirus encoding murine ADA (mADA) exhibited levels of mADA activity severalfold higher than the levels of the endogenous human ADA protein observed in normal human T lymphocytes. Strikingly, the long-term expression of the transgene was dependent on the activation status of the lymphocytes. This approach will have important applications in human gene therapy protocols targeting primary T lymphocytes.

Adenosine Deaminase↗