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Biomedical subjects

S Kitani

Publications and source records attributed to S Kitani.

At least 19 recordsLinked to original sources
PubMed2001

Gene replacement analysis of the butyrolactone autoregulator receptor (FarA) reveals that FarA acts as a Novel regulator in secondary metabolism of Streptomyces lavendulae FRI-5.

IM-2 [(2R,3R,1'R)-2-1'-hydroxybutyl-3-hydroxymethyl gamma-butanolide] is a gamma-butyrolactone autoregulator which, in Streptomyces lavendulae FRI-5, switches off the production of D-cycloserine but switches on the production of a blue pigment and several nucleoside antibiotics. To clarify the in vivo function of an IM-2-specific receptor (FarA) in the IM-2 signaling cascade of S. lavendulae FRI-5, a farA deletion mutant was constructed by means of homologous recombination. On several solid media, no significant difference in morphology was observed between the wild-type strain and the farA mutant (strain K104), which demonstrated that the IM-2-FarA system does not participate in the morphological control of S. lavendulae FRI-5. In liquid media, the farA mutant overproduced nucleoside antibiotics and produced blue pigment earlier than did the wild-type strain, suggesting that the FarA protein acts primarily as a negative regulator on the biosynthesis of these compounds in the absence of IM-2. However, contrary to the IM-2-dependent suppression of D-cycloserine production in the wild-type strain, overproduction of D-cycloserine was observed in the farA mutant, indicating for the first time that the presence of both IM-2 and intact FarA are necessary for the suppression of D-cycloserine biosynthesis.

Bacterial Proteins↗
PubMed2001

IgG-mediated histamine release from canine mastocytoma-derived cells.

BACKGROUND: Recent data suggest that normal tissue mast cells can express functional receptors for IgG under certain conditions. However, little is known about IgG receptor expression and functional consequences in mast cell neoplasms. METHODS: In this study, neoplastic mast cells were obtained from a dog with cutaneous mastocytoma (CM-MC) and from a dog with visceral mastocytoma (VI-MC). Both cell populations were characterized morphologically and functionally. RESULTS: Most cells proliferated constantly in suspension without particular supplements. Doubling times of CM-MC and VI-MC were 52.2 and 27.5 h, respectively. Both cell types were sensitive to formalin fixation, did not contain heparin and were tryptase and chymase positive. Electron microscopy showed fine granules with electron-dense content in both cell populations. The total histamine content of CM-MC and VI-MC was 0.25 and 0.10 pg/cell, respectively. Calcium ionophore A23187 and substance P induced dose-dependent histamine release, whereas compound 48/80 had no effect. Most significantly, both cell types, when sensitized with monomeric dog IgG, released histamine upon stimulation by anti-dog IgG. CONCLUSIONS: Dog mastocytoma-derived cells may be useful to study the regulation of neoplastic mast cell growth and differentiation, as well as IgG receptor-mediated activation in neoplastic mast cells. Further research is required to clarify the pathophysiological significance of constitutive expression of IgG receptors in neoplastic (canine) mast cells.

Animals↗
PubMed1999

Casein kinase II-like ectokinase activity on RBL-2H3 cells.

We studied the properties of the ectokinase activity on the outer cell surfaces of RBL-2H3 cells and examined the phosphorylation of exogenous substrates to clarify the substrate specificity of the ectokinases on RBL-2H3 cells. Among the several protein substrates tested, casein was the most strongly phosphorylated with [gamma-32P]ATP, and the net incorporation of 32P into casein was 0.65 pmol P/50 microg/10(6) cells. Casein kinase II peptide was also phosphorylated with [gamma-32P]ATP. The phosphorylation of casein and casein kinase II peptide was almost completely inhibited by the addition of 3 microg/ml of cell-impermeable K252b. Phosphorylation of casein and casein kinase II peptide was also observed by [gamma-32P]GTP. Western blot analysis using anti-casein kinase II antibody revealed a 44-kDa casein kinase band in the membrane fraction and Fc epsilonRI complexes. The immunofluorescence microscopic analysis using anti-casein kinase II antibody showed the existence of casein kinase II on the surface of the cells. This is the first report about the existence of ectokinase on mast cells.

Animals↗
PubMed1999

Novel polymorphism of the 5-lipoxygenase activating protein (FLAP) promoter gene associated with asthma.

The human 5-lipoxygenase activating protein (FLAP) gene is one of the key genes involved in the production of the cysteinyl-leukotrienes. We studied novel polymorphism of the FLAP promoter gene and attempted to clarify the relationship between this polymorphism and asthma. We sequenced the FLAP promoter region, containing the -170 to +46-bp sequence from the translational start codon, and found two homozygotes of novel alleles in the polyadenyl region which showed 21 A repeats and 18 A repeats, respectively. The frequency of the 21 A repeats was 52/71 (73.2%) in asthmatics and 39/71 (54.9%) in control subjects. The difference between these frequencies was statistically significant (P = 0.035). This is the first report of FLAP promoter gene polymorphism associated with asthma. Our data suggest that FLAP promoter gene polymorphism might play a crucial role in the pathogenesis of asthma.

5-Lipoxygenase-Activating Proteins↗
PubMed1999

In vitro analysis of the butyrolactone autoregulator receptor protein (FarA) of Streptomyces lavendulae FRI-5 reveals that FarA acts as a DNA-binding transcriptional regulator that controls its own synthesis.

FarA of Streptomyces lavendulae FRI-5 is a specific receptor protein for IM-2, a butyrolactone autoregulator that controls the production of a blue pigment and the nucleoside antibiotics showdomycin and minimycin. Gel shift assays demonstrated that FarA binds to the farA upstream region and that this binding is abolished in the presence of IM-2. The FarA binding sequence was localized by DNase I footprinting to a 28-bp sequence located approximately 70 bp upstream of the farA translational start site. High-resolution S1 nuclease mapping of farA transcripts revealed a putative transcription start site, located at an A residue positioned 64 bp upstream from the farA translation start codon and 4 bp downstream from an Escherichia coli sigma(70)-like -10 recognition region. The FarA-binding sequence overlaps this -10 region and contains the farA transcription initiation site, suggesting that FarA acts as a repressor that, in the absence of IM-2, represses transcription of farA.

4-Butyrolactone↗
PubMed1998

Expression of 5-lipoxygenase and 5-lipoxygenase-activating protein mRNAs in the peripheral blood leukocytes of asthmatics.

Leukotrienes are a family of arachidonic acid metabolites with potent biological activities such as bronchoconstriction and leukocyte chemotaxis. Recent evidence has demonstrated that the 5-lipoxygenase (5-LO) and 5-lipoxygenase-activating protein (FALP) products of arachidonic acid metabolism, leukotriene C4, D4 and E4, were increased in the serum and the urine of asthmatic patients. Therefore, we examined the expression of 5-LO and FLAP mRNAs in the peripheral blood leukocytes (PBL) of 10 asthmatics and 10 controls. Both 5-LO and FLAP mRNAs of PBL in the asthmatic group were found to be significantly increased compared with those in the control group. These data suggest that up-regulation of 5-LO and FLAP mRNAs might be involved in the increased leukotriene synthesis and play an important role in the pathogenesis of asthma.

5-Lipoxygenase-Activating Proteins↗
PubMed1997

Effect of an ectokinase inhibitor, K252b, on degranulation and Ca2+ signals of RBL-2H3 cells and human basophils.

We examined the effects of K252b, an ectoprotein kinase inhibitor of microbial origin, on the activation process of RBL-2H3 cells by cross-linking of IgE receptors by the endoplasmic reticulum Ca2+-ATPase inhibitor 2,5-di(tert-butyl)-1,4-hydroquinone or by the Ca2+ ionophore A23187. Analysis of phosphorylation of ectoproteins following IgE receptor cross-linking revealed that K252b mainly inhibited the phosphorylation of a 130-kDa protein. The inhibitor simultaneously inhibited degranulation and the sustained increase in the cytosolic calcium ion concentration even after addition of Ag. In contrast, K252b did not inhibit the increase in degranulation and cytosolic calcium ion concentration caused by stimulation with 2,5-di(tert-butyl)-1,4-hydroquinone and A23187. Permeation of K252b into RBL-2H3 cells, assessed by fluorescence intensity, was very low. K252b also inhibited degranulation caused by IgE receptor cross-linking in human basophils, but did not inhibit the degranulation caused by A23187. Thus, our findings suggest that the effects of K252b may be mediated by outer surface-bound or -anchored K252b-sensitive molecules on RBL-2H3 cells and human basophils, and that the phosphorylation of ectoprotein may involve a transmembrane influx of Ca2+ by IgE receptor cross-linking.

Basophils↗
PubMed1996

Surface expression of CD63 antigen (AD1 antigen) in P815 mastocytoma cells by transfected IgE receptors.

The surface expression CD63 antigen in rat basophilic leukemia cells (RBL-2H3) was observed after antigen stimulation by confocal fluorescence microscopy. The surface expression of CD63 antigen reflected the degranulation in RBL-2H3 cells. Then, we did the same experiments in P815 mastocytoma cells with transfected IgE receptors. The expression was observed in P815 cells with normal IgE receptors, but not in P815 variant cells with IgE receptors which were missing a C-terminal cytoplasmic domain of beta or gamma subunit. In addition, the expression in P815 cells with normal IgE receptors was mostly blocked by the pretreatment of herbimycin A. The results suggested that tyrosine phosphorylation of the C-terminal cytoplasmic domains of beta and gamma subunits was essential for degranulation.

Animals↗
PubMed1996

Nonreleasing basophils convert to releasing basophils by culturing with IL-3.

The extent of basophil histamine release initiated by IgE cross-linking stimuli has been known to vary greatly among donors. Studies on anti-IgE nonreleasing basophils are useful in understanding the IgE-specific control mechanism of mediator release. We attempted to determine (1) whether a mutation of Fc epsilon RI is present in nonreleasing basophils and (2) whether treatment with IL-3 converts anti-IgE nonreleasing basophils to releasing basophils. Basophils were purified from normal human blood and donors were divided into releasers (maximal histamine release > 5%) and nonreleasers (< 5%). The mutation of Fc epsilon RI alpha, beta, and gamma was evaluated by reverse transcriptase-polymerase chain reaction, and the DNA sequence was determined from amplified polymerase chain reaction products. Although antibodies against Fc epsilon RI failed to cause histamine release in anti-IgE nonreleasing basophils, no primary structural change of Fc epsilon RI was observed in nonreleaser basophils. After culturing with IL-3 for 7 days, nonreleasing basophils released histamine in response to anti-IgE, and dose-response curves of anti-IgE were equal in both releasers and nonreleasers. The conversion of nonreleasing basophils to releasing basophils was evident after 3 days of culture with IL-3. These findings indicate that nonreleasing basophils have recoverable defect(s) in the signal transduction pathway after IgE cross-linking.

Base Sequence↗
PubMed1996

The effect of okadaic acid on histamine release, cell morphology and phosphorylation in rat basophilic leukemia (RBL-2H3) cells, human basophils and rat peritoneal mast cells.

To study the involvement of serine/threonine phosphatase in the signal transduction of mast cells, we examined the effects of okadaic acid (OA), an inhibitor of type-1 and -2A phosphatase on histamine release, cell morphology, calcium influx and protein phosphorylation of rat basophilic leukemia (RBL-2H3) cells, human basophils and rat peritoneal mast cells. OA inhibited IgE-mediated histamine release from RBL-2H3 cells and human basophils dose-dependently. There was a remarkable enhancement of IgE-mediated histamine release when rat peritoneal mast cells were suboptimally challenged. OA induced a marked change of cell features, detached RBL-2H3 cells from plastic well and kept the 18- and 68-kD proteins phosphorylated. These findings show that phosphatase may play a role in the modulation of secretion in mast cells.

Animals↗
PubMed1996

Pharmacologic study of basophil histamine release induced by monocyte chemotactic protein-1 with kinase inhibitors.

Monocyte chemotactic protein-1 (MCP-1)/monocyte chemotactic activating factor has a potent histamine-releasing activity for basophils and is a major component of IgE-independent histamine-releasing factors (HRF). In this study, we examined the effect of a panel of kinase inhibitors on MCP-1-induced histamine release from human basophils to characterize the signaling pathway used by this chemokine. Genistein (3 micrograms/ml), an inhibitor of tyrosine kinase, inhibited MCP-1-induced histamine release by 44%. Wortmannin is a specific inhibitor of phosphatidylinositol 3 kinase (PI-3 kinase). It blocked MCP-1-induced histamine release with an IC50 of 3.3 x 10(-8) M indicating a role of PI-3 kinase in this reaction. KT5926, an inhibitor of myosin light chain kinase, also inhibited histamine release in response to MCP-1 with an IC50 of 10(-6) M. Staurosporine, a potent inhibitor of protein kinase C, although being not specific, augmented MCP-1-induced histamine release by 31.9% at 10(-6) M. These results indicate the possible involvement of a series of kinases, including PI-3 kinase, in the signal transduction pathway used by MCP-1.

Alkaloids↗
PubMed1995

Pharmacological study of stem-cell-factor-induced mast cell histamine release with kinase inhibitors.

Stem cell factor (SCF) is a ligand for c-kit receptor and has a critical role in the development of mast cells. In this study, we investigated the effect of a panel of kinase inhibitors on SCF-induced histamine release from rat peritoneal mast cells. Genistein, an inhibitor of tyrosine kinases, inhibited SCF-induced histamine release with IC50 of 1.6 x 10(-5) M. Wortmannin, an inhibitor of phosphatidylinositol 3'-kinase (PI3 kinase), inhibited histamine release stimulated with SCF dose-dependently with IC50 of 4 x 10(-9) M. KT5926, an inhibitor of myosin light chain (MLC) kinase, reduced histamine release with IC50 of 1.8 x 10(-7) M. Staurosporine, an inhibitor of protein kinases, also inhibited SCF-induced histamine release with IC50 of 6.5 x 10(-8) M. These results show the early involvement of tyrosine kinase and PI3 kinase and the possible role of MLC kinase in the late secretory phase in the signaling pathway used by SCF.

Alkaloids↗
PubMed1995

[Endoscopic endonasal surgery for postoperative maxillary cyst].

Endoscopic endonasal surgery was performed on 64 patients (69 sides) with postoperative maxillary cyst. We marsupialized the cyst in the inferior and/or middle meatus to enlarge it as much as possible. To facilitate an easier approach to the cyst wall in the inferior nasal meatus, some patients underwent submucous resection of the inferior nasal concha or inferior turbinectomy. Thirty-eight patients (44 sides) were followed for more than six months after surgery and a wide opening was confirmed in 36 (81.8%) of the 44 sides. Whether we should utilize an endonasal approach or a Caldwell-Luc approach depends mainly on the location of the medial wall of the cyst. We classified the cysts into medial, anterolateral and posterolateral types. Drawing a line between the anterior end of the inferior turbinate and the base of the lateral pterygoid process, on the axial plane of CT at the mid level of the inferior meatus, is the first stop. A medial cyst extends toward the midline across this imaginary line. A lateral cyst is subdivided into anterolateral and posterolateral based on the position of the center of cyst. The endoscopic endonasal approach resulted in excellent outcomes in medial and posterolateral cysts, while this approach was not found to be suitable for anterolateral cysts.

Adult↗
PubMed1994

[Experimental study on antidromic evoked potential of the facial nerve for clinical application].

Antidromic evoked potentials (AEPs) of the facial nerve were registered from the external auditory canal (EAC) of guinea pigs to clarify the origin of AEP and to compare diagnostic values of AEP with those of conventional evoked electromyography (eEMG). 1) The latency of AEP registered from EAC was compared with those from three points along the fallopian canal. The results showed that the latency from the pyramidal portion was almost equal to that from EAC. 2) AEPs were registered from EAC following sectioning of the intratemporal portion of the facial nerve at five points between the geniculate ganglion and the stylomastoid foramen. The waveform of the AEP was biphasic when the nerve was cut proximal to the pyramidal portion. It was monophasic when sectioned peripheral to that portion. These results, together with findings from experiment 1, indicate that AEP reflects the evoked potential generated around the pyramidal portion of the facial nerve, and that AEP is useful for the topodiagnosis of facial palsy. 3) AEP and eEMG were registered to assess changes in elicitability following compression of the facial nerve. Disappearance and reappearance of the AEP reflected well the function of the facial nerve as compared to the eEMG. This also indicates that AEP is a potentially sensitive and reliable diagnostic parameter for predicting the prognosis of facial palsy. 4) Registration of AEPs was attempted in three normal human subjects and in seven patients with Bell's palsy. AEP were recordable in all three normal men. Recording was however, possible in only two of seven patients on the involved side.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Adenomatous hyperplasia of the liver resembling focal nodular hyperplasia in patients with chronic liver disease.

Two nodules of hepatic adenomatous hyperplasia (AH) resembling focal nodular hyperplasia were found in two patients with cirrhosis or chronic active hepatitis. Imaging techniques suggested that the nodules were hepatocellular carcinoma. Pathological examination showed that the nodules (approximately 1.0 cm in diameter) were clearly demarcated from the surrounding liver tissue, and contained foci of scar-like fibrosis in the centre of the nodules. Microscopically, they contained portal tracts and fulfilled the criteria of AH. A large number of arteries were present in the central scar-like fibrosis as well as in the parenchyma of the nodules. There were foci of mildly atypical hepatocytes in one nodule but no cellular atypia in the other. Morphometric analysis showed that the cumulative luminal area of arteries per unit area was much greater in the nodules than in the extranodular liver tissues, while the cumulative luminal area of portal veins per unit area was much less in the nodules than in the extranodular liver tissues. Although the pathogenesis is unclear, these nodules might have developed through localized vascular changes associated with chronic liver disease, may have arisen from pre-existing arterial malformation, or may represent the early stages of angiogenesis in hepatocarcinogenesis.

Adenoma↗