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Biomedical subjects

K Okazaki

Publications and source records attributed to K Okazaki.

At least 73 records · Page 4Linked to original sources
PubMed2000

Downregulation of beta1 integrins by Ebola virus glycoprotein: implication for virus entry.

Filoviruses, including Ebola virus, are cytotoxic. To investigate the role of the Ebola virus glycoprotein (GP) in this cytopathic effect, we transiently expressed the GP in human kidney 293T cells. Expression of wild-type GP, but not the secretory form of the molecule lacking a membrane anchor, induced rounding and detachment of the cells, as did a chimeric GP containing its ectodomain and influenza virus hemagglutinin transmembrane-cytoplasmic domain. These results indicate that the GP ectodomain and its anchorage to the membrane are required for GP-induced morphologic changes in host cells. Since cell rounding and detachment could be associated with reduced levels of cell adhesion molecules, we also studied the expression of integrins, which are major molecules for adhesion to extracellular matrices, and found that the beta1 integrin group is downregulated by the GP. This result was further extended by experiments in which anti-beta1 monoclonal antibodies or purified integrins inhibited the infectivity of vesicular stomatitis virus pseudotyped with the GP. We suggest that integrins, especially the beta1 group, might interact with the GP and perhaps be involved in Ebola virus entry into cells.

Cell Line↗
PubMed2000

Characterization of Brassica S-haplotypes lacking S-locus glycoprotein.

Self-incompatibility (SI) in Brassica is regulated by a single multi-allelic locus, S, which contains highly polymorphic stigma-expressed genes, SLG and SRK. While SRK is shown to be the determinant of female SI specificity, SLG is thought to assist the function of SRK. Here we report that the SLG genes of self-incompatible S(18) and S(60) homozygotes of Brassica oleracea have an in-frame stop codon and a 23 bp deletion resulting in a frame-shift, respectively. The finding that these SLG genes do not encode functional SLG proteins suggests that SLG is not essential for SI. The possible role of SLG in SI was discussed.

Amino Acid Sequence↗
PubMed2000

Smad7 selectively interferes with different pathways of activin signaling and inhibits erythroid leukemia cell differentiation.

Smad family proteins are essential for transforming growth factor beta (TGF-beta) signal mediation downstream of a heteromeric complex of the type I and type II receptor serine/threonine kinases. A distant family member, Smad7, is expressed in most mammalian tissues and cells and prevents TGF-beta signaling. In this study, we examined the physiologic role of Smad7 in mediating the effects of activin, a member of the TGF-beta superfamily of peptides that functions in a number of processes, including blood-cell development. We report here that Smad7 expression is specifically absent in particular hematopoietic cells that respond to activin by differentiating into the erythroid lineage and that ectopic production of Smad7 causes mouse erythroid leukemia (F5-5) cells to become resistant to activin induction of erythroid differentiation. When coexpressed with type I activin receptor ActR-I or ActR-IB in concert with type II receptor ActR-II, Smad7 efficiently reduced an early transcriptional response mediated by ActR-I but had only a minimal effect on the response mediated by ActR-IB. In the presence of Smad7, overexpression of an activated form of ActR-IB, but not of an activated form of ActR-I, induced F5-5 cells to differentiate. These results suggest that Smad7 selectively interferes with the ActR-I pathway in activin signal transduction. The findings also indicate the existence of a novel activity of Smad7 that inhibits erythroid differentiation by blocking intracellular signaling of activin.

3T3 Cells↗
PubMed2000

The ActR-I activin receptor protein is expressed in notochord, lens placode and pituitary primordium cells in the mouse embryo.

ActR-I is a type I serine/threonine kinase receptor which has been shown to bind activin and bone morphogenetic proteins (BMPs). To study the function of ActR-I, we have generated novel monoclonal antibodies that specifically recognize the extracellular domain of mouse ActR-I. We examined the level of ActR-I protein during mouse development by immunohistochemistry. We found that in the embryonic body, ActR-I protein first appears in a restricted part of the primitive streak region and is present throughout the length of notochord. Furthermore, ActR-I protein is expressed in the facial sensory organ primordia, including eye area, otic vesicle and olfactory placode, which all contain invaginating ectoderm. In addition, ActR-I is produced in pituitary primordium (Rathke's pouch), mammary buds and the epithelial layer of branchial arches. Interestingly, in the lens placodes and in early Rathke's pouch, ActR-I protein is transiently localized at the apical surface of the epithelial cells, indicating the presence of an apical-basal asymmetry in these cells.

Activin Receptors, Type I↗
PubMed2000

mRNAs encoding zinc finger protein isoforms are expressed by alternative splicing of an in-frame intron in fission yeast.

We report here that a gene encoding a protein with three zinc fingers is expressed predominantly to produce a protein containing only two zinc fingers in the fission yeast Schizosaccharomyces pombe. A third zinc finger resides within the in-frame intron that is normally spliced out. By RT-PCR analysis, we detected a minor transcript encoding a protein with three zinc fingers. Such alternative splicing for assortment of zinc finger domains have been reported in animals and implicated in switching of the target genes expressed specifically during development. This is the first report of the occurrence of such zinc finger assortment in lower eucaryotes.

Alternative Splicing↗
PubMed2000

The polyubiquitin gene is essential for meiosis in fission yeast.

We isolated a novel sporulation-deficient mutant of Schizosaccharomyces pombe. The mutant did not have a mitotic growth defect but aborted meiosis at the first or the second division with condensed chromosomes that failed to separate, abnormal spindle(s), and disintegrated spindle pole bodies (SPBs). During the first division, the centromeres were pulled to near the spindle poles but condensed divalent chromosomes remained at the center. The failure to proceed to anaphase was also observed during a time-lapse recording of a SPB protein tagged with green fluorescent protein. The polyubiquitin gene ubi4(+), which encoded eight ubiquitins fused in tandem, complemented this mutant. The mutation, an A to G substitution, was identified within the ubi4(+) gene at the ATG initiation codon. Disruption of the ubi4(+) gene produced the same phenotypes. The ubi4(+) mRNA was strongly induced for meiosis. However, ubiquitin increases only slightly, suggesting that the role of the polyubiquitin gene is to supply ubiquitin that is consumed by unidentified mechanisms. Before the ubi4 mutant cells entered meiosis, ubiquitin was greatly decreased indicating that shortage of ubiquitin caused abortion of meiosis. This work provides insights for the role of polyubiquitin gene and importance of ubiquitination in SPB integrity at the meiotic divisions.

Amino Acid Sequence↗
PubMed2000

Constitutive activation of MAP kinase kinase (MEK1) is critical and sufficient for the activation of MMP-2.

We investigated the role of MEK1 signaling in MMP-2 activation by use of constitutive active/dominant negative forms of MEK1 and MEK1-specific inhibitor. We found that cell transformation with active forms of MEK1 dramatically increased secretion and proteolytic activation of MMP-2 and subsequently stimulated invasiveness of cells. Contrary, expression of dominant negative form of MEK1 in v-src-transformed cells or in Con A-activated cells resulted in the suppression of the augmented secretion and proteolytic activation of MMP-2. In addition, treatment of v-src-transformed cells with PD98059, a MEK1-specific inhibitor, strongly suppressed the secretion and activation of MMP-2, whereas treatment with wortmannin, a PI3 kinase inhibitor, showed no clear effect on MMP-2 secretion. Taken together, these results strongly suggest that MEK-MAP kinase signaling, but not PI3 kinase signaling, plays a critical role in the activation of MMP-2 secretion and, subsequently, in the invasiveness of v-src-transformed cells.

Animals↗
PubMed2000

Human papillomavirus type 33 DNA in breast cancer in Chinese.

BACKGROUND: The association between human papillomavirus (HPV) and anogenital tumors, especially cervical cancer, is well documented. However, it remains unclear whether there is also a correlation between HPV infection and human breast cancer. METHODS: We used PCR and Southern blot hybridization to analyze HPV-related DNA specimens from 32 cases of invasive ductal carcinoma operated upon in the Shanghai region of China. RESULTS: DNA derived from HPV33 was detected in 14 cases (43.8%). No HPV16 or HPV18 DNA was detected in any of the cases in this study. This is the first report demonstrating a correlation between HPV33 infection and breast cancer. CONCLUSIONS: Our results suggest that HPV33 infection may be involved in the pathogenesis of breast cancer in Chinese.

Adult↗
PubMed2000

FDG-PET of autoimmune-related pancreatitis: preliminary results.

The purpose of this retrospective study was to elucidate the fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) findings in autoimmune-related pancreatitis (AIP), which is a reversible chronic pancreatitis with an autoimmune cause. The study group comprised six patients with clinically diagnosed AIP. After 370 MBq (10 mCi) of FDG had been injected intravenously, the abdomen and/or the whole body was scanned at 1 h post injection in all patients, and scanning was repeated at 2 h in four patients. PET findings were evaluated visually and/or semiquantitatively using the standardized uptake value (SUV). In four of the six patients, PET demonstrated intense uptake in the whole pancreas, which appeared swollen on computed tomography, and the accumulation increased with time in three patients. In one patient, intense focal uptake in the pancreatic head was observed, and the accumulation decreased over time. In the remaining patient, no abnormal accumulation in the pancreas was observed. Follow-up PET scanning after steroid therapy was performed in three patients, and intense FDG uptake was no longer observed. Our preliminary data show that AIP can cause intense FDG uptake in the pancreas. This fact, and the benign status of the condition, should be kept in mind when making a diagnosis with FDG-PET in patients with pancreatic disorders.

Cell Survival↗
PubMed2000

Precursor genes of future pandemic influenza viruses are perpetuated in ducks nesting in Siberia.

Influenza A viruses of different subtypes were isolated from fecal samples of ducks in their nesting areas in Siberia in summer from 1996 to 1998. Phylogenetic analysis of the NP genes of the isolates in Siberia and those in Hokkaido, Japan on their flyway of migration from Siberia to the south in autumn revealed that they belong to the Eurasian lineage of avian influenza viruses. It is noted that the genes of the isolates in Siberia are closely related to those of H5N1 influenza virus strains isolated from chickens and humans in Hong Kong in 1997 as well as to those of isolates from domestic birds in southern China. The results indicate that influenza viruses perpetuated in ducks nesting in Siberia should have contributed genes in the emergence of the H5N1 virus in Hong Kong. Vaccine prepared from avirulent A/duck/Hokkaido/4/96 (H5N3) influenza virus was potent enough to protect mice from challenge with lethal dose of the pathogenic H5N1 virus [19]. Intensive surveillance study of aquatic birds especially in Siberia is, therefore, stressed to provide information on the future pandemic influenza virus strains and for vaccine preparation.

Animals↗
PubMed2000

Epitope mapping of the influenza A virus RNA polymerase PA using monoclonal antibodies.

To obtain reagents to functionally map the PA protein, we produced monoclonal antibodies specific to this protein. Twenty-two monoclonal antibodies reacting with PA protein in ELISA were divided into 10 groups on the basis of competitive binding patterns to this protein. Of these, seventeen monoclonal antibodies bound to PA polypeptide spanning amino acids 101-400 and three bound to that of amino acids 518-600, while the other two did not react with any PA polypeptides tested with the exception of full-length PA. Among these monoclonal antibodies, only five reacted with PA in A/PR/8/34 virus-infected cells in indirect immunofluorescence assay. Thus, we obtained monoclonal antibodies that recognize at least 10 distinct regions of the PA molecule. These monoclonal antibodies should be useful in dissecting functions of the PA protein.

Animals↗
PubMed2000

Mapping of functional domains on the influenza A virus RNA polymerase PB2 molecule using monoclonal antibodies.

Monoclonal antibodies against the PB2 of A/Puerto Rico/8/34 (A/PR/ 8/34) (H1N1) were prepared in order to define the functional domains of the RNA polymerase of influenza virus. The fifteen monoclonal antibodies that were generated were divided into 4 groups on the basis of ELISA binding to PB2 or its peptide fragments. Six Group I antibodies that bound to the PB2 N-terminal region (amino acids 1-104) did not inhibit transcription by the viral ribonucleoprotein complex. A single Group II antibody recognizing the region of amino acids 206-259 inhibited ApG-primed transcription. Groups III and IV antibodies bound to the C-terminal region of amino acids 660-759. Of these, Group III antibodies inhibited transcription. The present results identify multiple monoclonal antibody binding domains in PB2, two of which, when bound by antibodies, negatively affect viral RNA transcription.

Amino Acid Sequence↗
PubMed2000

Structure of the infected cell protein 0 gene of canine herpesvirus.

The canine herpesvirus infected cell protein 0 (CICP0) gene was sequenced. The CICP0 gene was transcribed as a 1.4 kb mRNA from the end of the unique long region nearby the internal repeat during early phase of productive infection of the virus. An open reading frame of the gene encodes a polypeptide of 333 amino acids. The RING finger domain and acidic transcriptional activation domain were found at the N-terminus and within the middle region in the deduced amino acid sequence, respectively, suggesting that the CICP0, like the ICP0 of herpes simplex virus 1, is a transactivating protein.

Amino Acid Sequence↗
PubMed2000

Autoimmune-related pancreatitis is associated with autoantibodies and a Th1/Th2-type cellular immune response.

BACKGROUND & AIMS: Although autoimmunity may be involved in some cases of pancreatitis, the mechanism is still unknown. To clarify this, we studied serum autoantibodies, subsets of lymphocytes, and the Th1/Th2 balance of cellular immune responses in patients with autoimmune-related pancreatitis (AIP). METHODS: Seventeen patients with AIP (8 men and 9 women; age, 53.2 +/- 13.0 years) were studied. Autoantibodies including antilactoferrin (ALF) or carbonic anhydrase II antibody (ACA-II) were examined using the enzyme-linked immunosorbent assay (ELISA) or the indirect fluorescein antibody method. Intracellular cytokines (interferon gamma and interleukin 4) and subtypes of peripheral blood lymphocytes were examined by flow cytometry and ELISA. RESULTS: More than one autoantibody was observed in all 17 patients. Serum antinuclear antibody was detected in 13 of 17 patients, ALF antibody in 13, ACA-II antibody in 10, rheumatoid factor in 5, and anti-smooth muscle antibody in 3, but antimitochondrial antibody in none. The serum levels of ACA-II and LF antibody were not correlated. HLA-DR(+)CD8(+) and HLA-DR(+)CD4(+) cells were significantly increased in peripheral blood (P < 0.05). CD4(+) cells producing interferon gamma and the secreted levels were significantly increased compared with those in controls (P < 0.05), but interleukin 4 was not increased. CONCLUSIONS: An autoimmune mechanism against CA-II or LF, and Th1-type immune response, may be involved in AIP.

Adult↗
PubMed2000

Simultaneous measurement of temperature and velocity maps by inversion recovery tagging method.

A new method, called the inversion recovery (IR) tagging method, for simultaneous measurement of temperature and velocity maps of flowing fluid has been developed. The present method employs a set of tagging pulses which acts as an inversion pulse of the conventional IR method, based on the temperature dependence of the spin-lattice relaxation of water proton in a fluid, and has the advantage of being able to compensate the reduction of the NMR signal intensity due to flow motion and to reduce the total time to measure these maps. First, the accuracy of the temperature measurement of stagnant doped water in a differentially heated cell using the conventional IR method, as the basic sequence of the IR tagging method, has been evaluated. The accuracy was within 10% of the temperature difference DeltaT = 17.2 degrees C and the measurable temperature resolution was within +/-0.5 degrees C. Then temperature and velocity maps of the flowing doped-water through a cooled pipe were measured simultaneously by the IR tagging method, and the accuracy of temperature measurement was evaluated. The accuracy obtained using the present method was within 15% of the temperature difference DeltaT = 15 degrees C.

Humans↗
PubMed2000

High-pressure magnetic resonance imaging up to 40 MPa.

A high-pressure vessel designed for use with commercial magnetic resonance imaging equipment at up to 40 MPa of pressure was used and tested. Special features of the vessel are the following: 1) 12.6 mm sample chamber i.d.; 2) only non-magnetic parts; 3) visible sample from the outside; 4) resistant to corrosive chemicals, and; 5) sample could be manually translated and rotated in situ. This apparatus was demonstrated through observation of CO(2) clathrate-hydrate growth in a water droplet injected into liquid CO(2) at 20 MPa.

Carbon Dioxide↗
PubMed2000

A patient with improvement of ulcerative colitis after appendectomy.

Recently, several retrospective studies have shown an inverse association between appendectomy and development of ulcerative colitis. We describe a 21-year-old man with distal ulcerative colitis and appendiceal involvement. The patient passed bloody stools continually during the 3 years before admission. Macroscopic and microscopic findings showed chronic moderate inflammation of the appendix and rectum. The ratio of CD4 to CD8 lymphocytes isolated from rectal and appendiceal mucosa was increased (4.3 and 3.8, respectively) compared with controls (n = 11; 1.0 in the rectum and 1.4 in the appendix). Clinical symptoms and colonoscopic and microscopic findings improved significantly after appendectomy. In addition, the amount of interferon gamma secreted from rectal lymphocytes was reduced to 89 pg/mL after surgery (before appendectomy, 254 pg/mL). However, interleukin 4 production was below detectable levels both before and after appendectomy. These findings suggest that appendectomy resulted in altered T-helper (Th)1/Th2 balance in this patient. In the 3 years since surgery, the patient has been in good condition without recurrence of symptoms. This is the first report demonstrating therapeutic benefit of appendectomy in a patient with ulcerative colitis and potential mechanistic relationship.

Adult↗