Biomedical subjects

K Okamoto

Publications and source records attributed to K Okamoto.

At least 433 records · Page 24Linked to original sources

PubMed1997

Reduced blood accumulation of biotinylated monoclonal antibody A7 after the subsequent administration of avidin.

Clear immunoscintigraphy with radiolabeled monoclonal antibodies (MAbs) requires a high tumor tissue/blood ratio of radioactivity. In this study, we attempted to obtain a high tumor tissue/blood ratio by the active removal of radiolabeled MAb from the circulation, using the avidin-biotin system. Biotinylated 125I-labeled MAb A7 was injected intravenously into nude mice bearing a human colon cancer (WiDr) xenograft. Avidin was injected 24 h later. The tumor tissue/blood ratio of radioactivity was almost four times that of controls. These results suggest that biotinylated 125I-labeled MAb A7 and avidin are potentially useful for the rapid immunodetection of human colon cancer.

Animals↗

PubMed1997

Phosphorylation of alphaB-crystallin in response to various types of stress.

Phosphorylation of alphaB-crystallin, a member of the hsp27 family, in human glioma (U373 MG) cells was stimulated by exposure of the cells to various stimuli, which included heat, arsenite, phorbol 12-myristate 13-acetate (PMA), okadaic acid, H2O2, anisomycin, and high concentrations of NaCl or sorbitol, but not in response to agents that elevated intracellular levels of cyclic AMP. Cells exposed to PMA together with okadaic acid yielded three bands of 32P-labeled alphaB-crystallin when immunoprecipitated samples were subjected to electrophoresis on an isoelectric focusing gel. All of the phosphorylated residues were identified as serine, an indication that three different serine residues can act as sites of phosphorylation in alphaB-crystallin. Structural analysis by mass spectrometry revealed that phosphorylation of alphaB-crystallin occurred at serines 19, 45, and 59. Dithiothreitol and staurosporine selectively inhibited the phosphorylation induced by arsenite and the phorbol ester, respectively. SB202190, an inhibitor of p38 mitogen-activated protein (MAP) kinase, suppressed the phosphorylation induced by arsenite, anisomycin, H2O2, sorbitol, NaCl, and heat shock, but not that induced by PMA and okadaic acid. The PMA-induced phosphorylation was selectively suppressed by an inhibitor of p44 MAP kinase kinase, PD98059. Although PMA and arsenite preferentially stimulated the phosphorylation of Ser-45 and Ser-59, respectively, as determined with antibodies that recognized the respective phosphorylated forms of alphaB-crystallin, all three sites were phosphorylated in response to each stimulus. These results suggest that p38 MAP kinase or p44 MAP kinase might be involved in the signal transduction cascade that leads to the phosphorylation of alphaB-crystallin. The phosphorylation of alphaB-crystallin was also enhanced in the heart and diaphragm when rats were exposed to heat stress (42 degrees C for 20 min).

Animals↗

PubMed1997

PACAP stimulates pancreatic exocrine secretion via the vagal cholinergic nerves in sheep.

The present study evaluates the possible role of the vagus nerves in mediating the stimulatory effect of PACAP-27, PACAP-38 and VIP on the exocrine pancreas, especially on enzyme secretion which is atropine sensitive in sheep. The animals were equipped with two cannulae into the common bile duct, a duodenal cannula, and a ruminal cannula under anesthesia. The bilateral cervical vagus nerves were coiled with a cooling device. In conscious animals, the peptides were infused intravenously for 10 min at 10 pmol kg(-1)min(-1) in phase II of the duodenal migrating motor complexes and the same peptide infusion was repeated in the reversible cooling blockade of the vagus nerves. Increment in fluid secretion was not significantly altered by the vagal blockade in all the peptide infusions, while increment in bicarbonate ion by only PACAP-27 was inhibited by the vagal blockade. Increments in protein and amylase output decreased significantly to 32.0+/-5.0 and 23.2+/-2.6% in PACAP27, and to 26.1+/-7.7 and 20.8+/-6.4% in PACAP-38 in the vagal blockade, but the increments by VIP did not decrease. These results demonstrate that circulating PACAP stimulates pancreatic enzyme secretion via the vagal cholinergic preganglionic neurons in sheep, suggesting the central action of PACAP.

Amylases↗

PubMed1997

Analysis of the McLeod syndrome gene in three patients with neuroacanthocytosis.

McLeod syndrome is a rare X-linked disorder involving neurological defects and acanthocytosis. We examined the XK gene in three patients with neuroacanthocytosis, one of whom had cardiomyopathy, and his symptoms were very similar to those of McLeod syndrome. We found two new transversions (C to G at codon 204 and G to C at codon 205) in exon 3 in all those cases. However, the transversion at codon 205 was found in all 70 Japanese normal subjects and four non-Japanese (two Caucasian males, one Chinese female and one Micronesian female) and that at codon 204 was also detected in all 14 normal Japanese males and the four non-Japanese. These findings suggest that they are not the cause of McLeod syndrome, but normal polymorphisms which have not been reported. Moreover, there is a possibility that patients with neuroacanthocytosis similar to McLeod syndrome exist without the XK gene abnormalities.

Acanthocytes↗

PubMed1997

Lysosomal generation of amyloid beta protein species in transgenic mice.

Soluble amyloid beta protein (A beta)1-40 and highly amyloidogenic A beta 1-42/43 were immunocytochemically labeled in lysosomes of acinar cells and macrophages in the pancreas of transgenic mice systemically expressing a C-terminal fragment of the A beta precursor. A beta 1-42/43 and long A beta species extending their C-termini were detected in the detergent-insoluble fraction. Immunoreactivity of cathepsin D was markedly increased in lysosomes filled with A beta fibrils. These findings indicated that A beta 1-40, A beta 1-42, A beta 1-43 and longer A beta species were generated in the lysosomes of the transgenic pancreas, and suggested that the activation of cathepsin D, a candidate gamma-secretase, leads to acceleration of A beta amyloid formation.

Amyloid beta-Protein Precursor↗

PubMed1997

[The clinicopathological features and operative results in a cancer of the remnant stomach--risk and prevention of cancer after partial gastrectomy].

The clinicopathological features and operative results were analyzed in 21 patients undergoing an operation for cancer of the remnant stomach between 1979 and 1997. The twenty-one patients were divided into two groups: Group A; n = 9: who had undergone a gastrectomy for benign gastric disease, Group B; n = 12: who had undergone the same operation for gastric cancer. In Group A, the interval between the first gastrectomy and the second was longer than in Group B. In both groups, a large number of advanced cancers (n = 16, 76.2%) and undifferentiated carcinomas (n = 15, 71.4%) were seen. Five-year-survival rates in Group A and Group B were 23.7%, 19.0%, respectively. The incidence of gastric stump cancer following partial gastrectomy was 80% in the patients on whom Billroth II reconstruction had been performed after gastrectomy. It is suggested that the residual stomach in the Billroth II reconstruction patients is susceptible to cancer development. Consideration of the reconstruction method and a systemic follow-up is needed to improve a prognosis.

Aged↗

PubMed1997

Epigenetic changes at the insulin-like growth factor II/H19 locus in developing kidney is an early event in Wilms tumorigenesis.

Relaxation of imprinting at the insulin-like growth factor II (IFG-II)/H19 locus is a major mechanism involved in the onset of sporadic Wilms tumor and several other embryonal tumors. The high prevalence of histologically abnormal foci in kidney adjacent to Wilms tumors suggests that tumor-predisposing genetic/epigenetic lesion might also be found at high frequency in Wilms tumor-bearing kidneys. Focusing on Wilms tumors with relaxation of IFG-II imprinting, we determined the frequency of epigenetic change at the IFG-II/H19 locus in adjacent kidney. In all kidneys adjacent to these Wilms tumors, we detected substantial mosaicism for a population of cells with relaxation of IFG-II imprinting and biallelic H19 methylation, regardless of whether the patient had a tumor-predisposing syndrome or not. The high proportion of epigenetically modified cells among "normal" tissue indicates that the epigenetic error occurred very early in development, before the onset of Wilms tumor. Not only does this suggest that the major Wilms tumor-predisposing event occurs within the first few days of development, but it also suggests that sporadic Wilms tumor may represent one end of a spectrum of overgrowth disorders characterized by mosaic epigenetic change at the IFG-II/H19 locus.

Alleles↗

PubMed1997

Cloning of poly(3-hydroxybutyrate) depolymerase from a marine bacterium, Alcaligenes faecalis AE122, and characterization of its gene product.

A DNA fragment that carries the gene coding for poly(3-hydroxybutyrate) (PHB) depolymerase was cloned from the chromosomal DNA of Alcaligenes faecalis AE122 isolated from seawater. The open reading frame encoding the precursor of the PHB depolymerase was 1905 base pairs (bp) long, corresponding to a protein of 635 amino acid residues (M(r) = 65,208). The promoter site, which could be recognized by Escherichia coli RNA polymerase, was upstream from the gene, and the sequence adhering to the ribosome-binding sequence was found in front of the gene. The deduced amino acid sequence agreed with the N-terminal amino acid sequence of the purified PHB depolymerase from amino acid 28 onwards. Analysis of the deduced amino acid sequence revealed the domain structure of the protein; a signal peptide of 27 amino acids long was followed by a catalytic domain of about 400 amino acids, a fibronectin type III module sequence, and a putative substrate binding domain. The molecular mass (62,526) of the mature protein deduced from the nucleotide sequence was significantly lower than the value (95 kDa) estimated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but coincided well with the value (62,426) estimated from matrix-assisted laser desorption ionization mass spectra. By comparison of the primary structure with those of other PHB depolymerases, the substrate binding domain was found to consist of two domains, PHB-specific and poly(3-hydroxyvalerate)-specific ones, connected by a linker region. The PHB depolymerase gene was expressed in Escherichia coli under the control of the tac promoter. The enzyme expressed in E. coli was purified from culture broth and showed the same catalytic properties as the enzyme from A. faecalis.

Alcaligenes↗

PubMed1997

Memory disturbance and hippocampal degeneration induced by continuous intraventricular infusion of a protease inhibitor, leupeptin.

Effects of a protease inhibitor, leupeptin, on the memory function and the morphological changes in the hippocampus were examined in rats. The leupeptin was infused by an implanted-osmotic minipump into the lateral ventricle of the rats for 14 days. The acquisition and the maintenance of memory were evaluated by a step-down passive avoidance task. The control rats, infused with an artificial cerebral spinal fluid, showed good retention for the passive avoidance training for 21 days after training. The leupeptin-treated rats showed good retention for 7 days following training; however, pronounced impaired retention was observed on day 10 and thereafter. These rats were accompanied by a degeneration of the dentate gyrus in the histological examinations on Days 14 and 21. The granule cells in the dentate gyrus of the hippocampus appeared much more eosinophilic pyknotic. Numerous eosinophilic spherical structures of the cell processes were seen in the neuropil beneath the granule cell layer. Electron microscopic examination disclosed a marked accumulation of lipofuscin-like granules in the perikaryon of the cells and in the dendrites and the axons. These findings suggest that the memory impairment is closely related to the degeneration of the dentate gyrus in the hippocampus in the leupeptin-treated rats.

Animals↗

PubMed1997

Characterization of a Dictyostelium factor that acts synergistically with DIF to induce terminal stalk cell differentiation.

The differentiation of Dictyostelium prestalk cells is induced by the chlorinated hexaphenone DIF-1 and their maturation into stalk cells at culmination occurs by activation of the cAMP-dependent protein kinase (PKA). Medium harvested from developing Dictyostelium cells will act synergistically with DIF-1 to induce prestalk cell differentiation in a low-density monolayer assay (Yamada and Okamoto, 1994). Using HPLC, we have partially purified from such conditioned medium an activity we term STIF (stalk-inducing factor). It is hydrophilic and of low molecular weight. There are multiple classes of prestalk cells, which are defined by their patterns of expression of the ecmA and ecmB genes and that can be further subcategorized because they utilize different elements within the promoters of the two genes. We show that, in a monolayer assay, STIF acts synergistically with DIF-1 to induce ecmB gene expression via promoter elements that are normally activated strongly only in cells that have entered the stalk tube and which are therefore committed to differentiate into stalk cells. The combination of STIF and DIF-1 also induces morphological maturation of prestalk cells into stalk cells but does not efficiently induce expression of ecmA: a gene that is selectively expressed in cells within the anterior, prestalk region of the slug. Inactivation of PKA, by cell type-specific expression of a dominant inhibitor, represses the action of STIF. These data suggest that STIF is an extracellular signal that acts to induce the terminal differentiation of stalk cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1997

Human p57(KIP2) defines a new imprinted domain on chromosome 11p but is not a tumour suppressor gene in Wilms tumour.

Mouse p57(Kip2) arrests cells in G1 by functioning as a strong inhibitor of several G1 cyclin/Cdk complexes (Lee et al., 1995; Matsuoka et al., 1995; Sherr and Roberts, 1995). Human p57(KIP2) has been suggested to be a tumour suppressor gene because of its location at 11p15.5 which frequently undergoes maternal allele LOH in several types of cancer (Matsuoka et al., 1995; Sherr and Roberts, 1995; Hatada and Mukai, 1995). This suggestion was supported by the discovery that mouse p57(Kip2) is imprinted with expression from only the maternally inherited allele (Hatada and Mukai, 1995). Interestingly, p57(KIP2) is several hundred kilobases from the imprinted H19 and IGF2 genes which are involved in growth regulation (Hoovers et al., 1995). Here we show that human p57(KIP2) is imprinted with expression from the maternal allele. However, unlike the mouse, the imprinting is incomplete with significant expression from the paternal allele depending on the tissue examined. We have also shown that the imprinting of p57(KIP2) occurs independently of the H19/IGF2 domain and thus there must be at least two imprinted domains in 11p15.5. Finally, by examining Wilms tumours we have shown that following maternal 11p LOH, p57(KIP2) was expressed from the paternal allele. Therefore, p57(KIP2) cannot function as an imprinted tumour suppressor gene, at least in Wilms tumour.

Adult↗

PubMed1997

Highly selective aldose reductase inhibitors. 3. Structural diversity of 3-(arylmethyl)-2,4,5-trioxoimidazolidine-1-acetic acids.

Accumulation of intracellular sorbitol, the reduced product of glucose, catalyzed by aldose reductase (AR) (EC 1.1.1.21), is thought to be the cause of the development of diabetic complications. Our attention is focused on finding compounds which inhibit AR without significantly inhibiting aldehyde reductase (ALR) (EC 1.1.1.2). The uracil or 2,4-dioxoimidazolidine skeleton having the benzothiazolyl or 4-chloro-3-nitrophenyl group as an aryl part indicated not only extremely high AR inhibitory activity but also AR selectivity. The ratio of IC50(ALR)/IC50(AR) of 3-[(5-chlorobenzothiazol-2-yl)methyl]-1,2,3,4-tetrahydro-2,4- dioxopyrimidine-1-acetic acid (47d) was more than 17 500. The uracil skeleton with the benzothiazolyl moiety seemed to be the best combination for selective AR inhibition.

Acetates↗

PubMed1997

Cytotoxicity of platinum (II) dinuclear complexes with 1-alkylthymine ligands against mouse sarcoma 180 cells.

We synthesized five platinum (II) dinuclear complexes containing 1-alkylated thymines. Two of the 1-alkylated thymine, 1-MeThy and 1-EtThy, complexes afforded good crystals. The X-ray structures of these complexes were determined. The 1-MeThy complexes has a head-to-head (H-H) arrangement, while the 1-EtThy complex has a head-to-tail (H-T) arrangement. The 1-MeThy complex (H-H) shows high electrophilicity against chloride anion (CI-) and high cytotoxicity against mouse sarcoma 180 (S-180) cells in vitro. The 1-EtThy complex (H-T) is inactive. The other 1-MeThy complex does not produce CDDP in the reaction with chloride ion and is inactive against the S-180 cell line. This complex is assumed to have an H-T arrangement. Similarly, two different 1-Pr(n)Thy complexes, one with high electrophilicity and cytotoxicity and the other without, must have an H-H and H-T arrangement, respectively. For comparison, we investigated six complexes, 1-methyluracil (1-MeUra) (H-H) dimer, alpha-pyridone (H-T) dimer, alpha-pyridone blue tetramer (PPB), 1-methylcytosine (1-MeCyt) (H-T) dimer, acetate dimer, and 1-MeUra monomer complexes. The alpha-pyridone (H-T), PPB, 1-MeCyt (H-T) dimer, and 1-MeUra monomer complexes are inert to chloride ion and inactive against mouse sarcoma S-180. The 1-MeUra (H-H) dimer and acetate dimer complexes show high electrophilicity and high cytotoxicity. Cellular accumulation of the platinum complexes phenomenally shows that all are incorporated to cancer cells to a lesser extent than CDDP. The relationships between the accumulation, the electrophilicity, and the interaction of these complexes with proteins are discussed.

Alkylation↗

PubMed1997

Severe thrombocytopenia suggesting immunological mechanisms in two cases of vivax malaria.

Case 1: A 27-year-old woman, referred to our hospital because of relapsing fever after travel to Thailand, was given a diagnosis of vivax malaria. Clinical investigation revealed thrombocytopenia, elevated platelet-associated IgG (PAIgG), and negative antibody against Plasmodium vivax antigen. After antimalarial treatment, the levels of both the platelets and PAIgG returned to normal. Case 2: A 28-year-old Sri Lankan man was admitted to our hospital with a complaint of fever. The patient had thrombocytopenia, elevated PAIgG, and positive antibody against Plasmodium vivax antigen. He contracted malaria in Sri Lanka about 6 months prior to this admission. After treatment, the platelet count and PAIgG level returned to normal. In these two cases, high levels of PAIgG may have been involved in the development of the thrombocytopenia. In the first patient, in particular, the thrombocytopenia was thought to be induced by some immunological mechanism prior to the detection of antimaralial antibodies in serum.

Adult↗

PubMed1997

Peritoneal lymphatic stomata of the diaphragm in the mouse: process of their formation.

BACKGROUND: Lymphatic stomata are channels connecting the peritoneal cavity with the lymphatics in the diaphragm. The process of sequential formation of the stomata has not been studied. The objective of this study was to examine the morphogenesis of the lymphatic stomata in mice. METHODS: Ultrathin sections of diaphragms from ddY mice obtained on embryonic day 18 and postnatal days 0, 4, and 10 were observed with a transmission electron microscope. RESULTS: By embryonic day 18 and postnatal day 0, lymphatics were already observed in the submesothelial connective tissue on the peritoneal side of the fetal diaphragm. The lymphatic endothelial cells, but not the mesothelial cells covering the diaphragm, protruded short cytoplasmic processes into the submesothelial connective tissue, and these almost reached the basal surfaces of individual mesothelial cells. By postnatal days 4 and 10, the lymphatic endothelial cells frequently protruded cytoplasmic processes into the submesothelial connective tissue, and the endothelial cell processes broke the continuity of both the basal lamina beneath the mesothelial cells and the submesothelial connective tissue. Neighboring endothelial processes formed a pair of U-shaped folds that were connected with each other via intercellular junctions at the apexes of the U-shaped folds. The disassembly of the intercellular junctions between the U-shaped folds was observed, and the basal surface of the mesothelial cell faced the lymphatic lumen. Dehiscence of the intercellular junctions between the mesothelial cells overlaying the lymphatics was observed, and lymphatic stomata were present. On the pleural side of the diaphragm, lymphatics were already present on embryonic day 18, but it was not observed that the endothelial process spanned the submesothelial connective tissue to the basal surface of the mesothelial cell. CONCLUSIONS: These results suggest the following process of the formation of the lymphatic stomata. (1) Neighboring lymphatic endothelial cells span the submesothelial connective tissue to the basal surfaces of mesothelial cells. (2) The lymphatic stomata are formed by the disassembly of the intercellular junctions between the neighboring endothelial cells and between the mesothelial cells overlying the endothelial cells.

Age Factors↗

PubMed1997

Prostaglandins stimulate the stress-induced synthesis of hsp27 and alpha B crystallin.

The effects were examined of various prostaglandins (prostaglandin A1, A2, J2, E2, and D2) on the stress-induced accumulation of hsp27 and alpha B crystallin in C6 rat glioma cells. The levels of hsp27 and alpha B crystallin, which were determined by specific immunoassays, were low in cells in confluent cultures. The levels of the two proteins increased after exposure of cells to heat (42 degrees C for 30 min) or arsenite (50 microM for 1 h). Cells exposed to 10 microM each of prostaglandin A1, A2, or J2 for 1 h resulted in stimulation of the binding to the heat shock element (HSE) of heat shock transcription factor (HSF). However, there was no phosphorylation-dependent mobility shift of HSF1 and no subsequent increase in the transcription and translation for hsp27, alpha B crystallin, and hsp70. When cells were exposed to arsenite in the presence of 10-40 microM prostaglandin, the accumulation of hsp27 and alpha B crystallin in cells was enhanced markedly. The levels of hsp70 also increased in cells that had been treated with arsenite in the presence of a prostaglandin, as estimated by Western blot analysis. Northern blot analysis revealed that the expression of messenger RNAs (mRNAs) for hsp27, alpha B crystallin, and hsp70 was enhanced in cells that had been exposed to arsenite in the presence of each prostaglandin. Similar stimulatory effects of prostaglandins also were observed in the case of the heat-induced responses of hsp27, alpha B crystallin, and hsp70. Gel mobility shift assays revealed that each prostaglandin prolonged the arsenite-induced binding of HSF to HSE. These results suggest that the pharmacological dose of prostaglandins stimulates the stress-induced synthesis of stress proteins via activation of the HSF.

Animals↗

PubMed1997

Inhibition of rheumatoid synovial fibroblast proliferation by antisense oligonucleotides targeting proliferating cell nuclear antigen messenger RNA.

OBJECTIVE: To evaluate the feasibility of antisense oligonucleotides as therapeutic agents to inhibit synovial cell growth in rheumatoid arthritis (RA). METHODS: Fibroblast-like cells established from RA synovium were stimulated with interleukin-1beta (IL-1beta) and treated with antisense or sense oligonucleotides targeting proliferating cell nuclear antigen (PCNA) messenger RNA (mRNA). Proliferation of these cells was determined by 3H-thymidine incorporation. Effects of antisense oligonucleotides on the expression of mRNA and protein were evaluated by reverse transcriptase-polymerase chain reaction and immunohistochemical staining, respectively. RESULTS: Antisense oligonucleotides targeting PCNA inhibited IL-1-stimulated fibroblast proliferation, whereas sense oligonucleotides had no effect. Both mRNA and protein levels of PCNA were suppressed in the cells treated with antisense oligonucleotides, indicating that the antiproliferative effect was occurring through an antisense mechanism. CONCLUSION: These results suggest that antisense strategies designed to suppress PCNA expression have potential use as therapeutic agents for RA.

Arthritis, Rheumatoid↗

PubMed1997

Selective activation of the JNK/AP-1 pathway in Fas-mediated apoptosis of rheumatoid arthritis synoviocytes.

OBJECTIVE: To evaluate the Fas-dependent signaling pathway, we examined the involvement of protein tyrosine phosphorylation and the DNA binding activity of AP-1 in rheumatoid arthritis (RA) cultured synovial cells. METHODS: The number of dead cells was counted after treatment with anti-Fas antibody in the presence of protein tyrosine kinase or phosphatase inhibitor. Protein tyrosine phosphorylation in synoviocytes after Fas ligation was examined by immunoblot and immunoprecipitation analyses. The DNA binding activity of AP-1 was examined by electrophoretic mobility shift assay. RESULTS: Treatment with the protein tyrosine phosphatase inhibitor, orthovanadate, significantly enhanced the apoptosis of RA synoviocytes after Fas ligation. Ligation of the Fas molecule on RA synoviocytes induced a rapid tyrosine phosphorylation of JNK (c-Jun amino-terminal kinase) and formation of the AP-1 transcription factor. CONCLUSION: Our results strongly suggest that the JNK/AP-1 signaling pathway is activated during the process of Fas-mediated apoptosis of RA synovial cells.

Apoptosis↗