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Biomedical subjects

K Okazaki

Publications and source records attributed to K Okazaki.

At least 235 records · Page 13Linked to original sources
PubMed1995

Mycobacteria in the intestine of Japanese patients with inflammatory bowel disease.

OBJECTIVES: It is still controversial whether or not a mycobacterial infection may be a cause of Crohn's disease. Mycobacterium paratuberculosis may be very difficult to detect using routine culture techniques. To clarify this, we detected mycobacterial DNA in patients with inflammatory bowel disease. METHODS: IS900 sequences highly specific to M. paratuberculosis and the groEL gene encoding a conserved mycobacterial antigen were studied in colonic mucosa using polymerase chain reaction (PCR). PCR products were analyzed by Southern blot hybridization. RESULTS: IS900 sequences were detected in all (100%) of 10 patients with Crohn's disease, in 11 (61.1%) of 18 patients with ulcerative colitis, and in 14 (87.5%) of 16 control patients with noninflammatory bowel disease. All IS900 positive samples had groEL PCR products. CONCLUSIONS: Our results, on the basis of the prevalence, do not support the hypothesis that M. paratuberculosis is involved in the pathogenesis of Crohn's disease.

Adolescent↗
PubMed1995

[Anatomical study of the ligaments in the occipito-atlantoaxial complex].

To investigate the role of the ligamentous complex in the stability of the atlanto-axial joint, the macroscopic anatomy of the occipito-atlanto-axial complex was studied in 44 cadavers involving the cruciate ligament of atlas, alar ligament, and the anterior atlanto-axial ligament (AADL). The transverse ligament (TL) had two layers, one was membranous tissue and the other was ligamentous. The mean length of the TL was 19.7 mm (range 14-25 mm). The TL was significantly longer in males than in females. The diameter of the TL was thinnest at the centre (mean 2.0 mm, range 1-5 mm). The thicker ligaments were significantly larger in diameter. The alar ligament (AL) was dissected and examined in all cadavers. The direction of the AL ran postero-laterally. This ligament was divided into five types according to the fiber orientation. Type 1 was separated type in its origin at the dens. Type 2 was partially connected type. Type 3 was totally connected with a covered dens tip. Type 4 was totally connected but did not cover the dens tip. Type 5 was a combined type of Type 3 covering Type 1. The fiber direction of the AL was divided into three types; caudocranial type, horizontal type, and craniocaudal type. The AADL was examined in 24 specimens (60%). This ligament existed bilaterally in 18 specimens (45%) and hemilaterally in 6 (15%). The right side only was examined in 2 specimens (5%) and the left side only in 4 specimens (10%). In 6 specimens, the orientations of this ligament was identified and the shape was found to be thin. From these results, it was considered that not only TL, but also the AL and AADLs played an important role in stabilizing the atlanto-axial complex.

Adult↗
PubMed1995

A light and scanning electron microscopic evaluation of electro-discharge-compacted porous titanium implants in rabbit tibia.

This study used light and scanning electron microscopic (SEM) histomorphometric methods to quantitate the rate of osseointegration of totally porous titanium alloy (Ti-6Al-4V) implants prepared by a novel fabrication technique--electrodischarge compaction (EDC). EDC was used to fuse 150-250-micrometer spherical titanium alloy beads into 4 X 6 mm cylindrical implants through application of a 300-microsecond pulse of high-voltage/high-current density. Two sterilized implants were surgically placed into each tibia of 20 New Zealand white rabbits and left in situ for periods corresponding to 2, 4, 8, 12, and 24 weeks. At each time point, 4 rabbits were humanely killed, and the implants with surrounding bone were removed, fixed, and sectioned for light and SEM studies. The degree of osseointegration was quantitated by means of a True Grid Digitizing Pad and Jandel Scan Version 3.9 software on an IBM PS/2 computer. The total pore area occupied by bone was divided by the total pore area available for bone ingrowth, and a Bone Ingrowth Factor (BIF) was calculated as a percent. The light microscopic results showed BIFs of 4% at week 2, 47% at week 4, 62% at week 8, 84% at week 12, and greater than 90% at week 24. The SEM results showed BIFs of 5% at week 2, 34% at week 4, 69% at week 8, 75% at week 12, and in excess of 90% at week 24. The results of this study show that EDC implants are biocompatible and support rapid osseointegration in the rabbit tibia and suggest that, after additional studies, they may be suitable for use as dental implants in humans.

Alloys↗
PubMed1994

Essential residues in V(D)J recombination signals.

Recombination signal sequences for V(D)J joining consist of a conserved heptamer (CACAGTG) and a nonamer (ACAAAAACC) separated by a spacer of a constant length (12 bp or 23 bp). In the present study, we have analyzed various recombination signal mutations for their effects in V(D)J joining. Using a retroviral vector, we introduced mutant substrates stably into pre-B cells, and assayed recombination using the lacZ gene as a reporter. This method allowed us to study recombination in a single copy within the context of the host cell chromosome. Because this assay did not show any detectable background, it was quite useful in the analysis of low level recombinations. In the heptamer, mutations in the first three residues severely dropped the joining rates. Among them, the first residue adjacent to the recombination site was found to be most essential. Although mutations in the heptamer reduced the joining rate to various extents, they did not lower the site-specificity of recombination. With regard to the nonamer, the presence of three consecutive A residues was necessary for efficient recombination. Furthermore, the nucleotides flanking the A-rich core needed to be other than A residues, probably marking the border of the A-stretch. This may be important when the recombinase measures the distance between the heptamer and the nonamer to satisfy the 12/23-bp spacer rule.

Animals↗
PubMed1994

Differential distribution of neurocalcin isoforms in rat spinal cord, dorsal root ganglia and muscle spindle.

The cellular distribution of neurocalcin isoforms in rat spinal cord, dorsal root ganglia and muscle spindle was examined using immunohistochemical techniques and two antibodies against different isoforms. In the study using the antibody against the purified neurocalcin from bovine brain, nerve fiber terminals and the cytoplasm of small-sized neurons in the posterior horn, some medium-sized neurons and numerous axons were strongly stained. In dorsal root ganglia, the cytoplasm of various-sized neurons, including about 40% of the total neurons, was also stained. Sensory nerve endings in muscle spindle were immunopositive. When the antibody against the expressed neurocalcin delta was applied, nuclei of the neurons were mainly stained in the spinal cord and dorsal root ganglion. The cytosol of glial cells but not axons in white matter showed neurocalcin delta-like immunoreactivity against the antibody. These findings suggest that each of the differently located isoforms may play a distinct role in Ca2+ signaling in sensory systems.

Amino Acid Sequence↗
PubMed1994

A synthetic peptide deduced from the sequence in the cross-region of laminin A chain mediates neurite outgrowth, cell attachment and heparin binding.

Synthetic peptides from the cross-region of the laminin A chain were prepared and tested for their biological activities, especially for neurite outgrowth. A synthetic 8-mer peptide (designated LMA-5) in the cross-region of the laminin A chain was found to promote neurite outgrowth in PC12 cells and cerebellar microexplant cultures. Furthermore, this peptide mediated cell attachment and heparin binding. In addition, an antibody against peptide LMA-5 inhibited laminin- and LMA-5-mediated cell attachment. This antibody also inhibited more than half of the LMA-5-promoted neurite outgrowth in cerebellar microexplant cultures. These data suggest that peptide LMA-5 is one of the active sites in laminin that regulate cell behaviour including neurite outgrowth, cell attachment and heparin binding.

Amino Acid Sequence↗
PubMed1994

Parthenogenetic activation of oocytes in c-mos-deficient mice.

In Xenopus the c-mos proto-oncogene product (Mos) is essential for the initiation of oocyte maturation, for the progression from meiosis I to meiosis II and for the second meiotic metaphase arrest, acting as an essential component of the cytostatic factor CSF. Its function in mouse oocytes is unclear, however, as is the biological significance of c-mos mRNA expression in testes and several somatic tissues. We have generated c-mos-deficient mice by gene targeting in embryonic stem cells. These mice grew at the same rate as their wild-type counterparts and reproduction was normal in the males, but the fertility of the females was very low. The c-mos-deficient female mice developed ovarian teratomas at a high frequency. Oocytes from these females matured to the second meiotic metaphase both in vivo and in vitro, but were activated without fertilization. The results indicate that in mice Mos plays a role in the second meiotic metaphase arrest, but does not seem to be essential for the initiation of oocyte maturation, spermatogenesis or somatic cell cycle.

Animals↗
PubMed1994

Suppression of DNA replication via Mos function during meiotic divisions in Xenopus oocytes.

Meiosis is characterized by the absence of DNA replication between the two successive divisions. In Xenopus eggs, the ability to replicate DNA develops during meiotic maturation, but is normally suppressed until fertilization. Here we show that development of the DNA-replicating ability depends on new protein synthesis during meiosis I, and that mere ablation of the endogenous c-mos product Mos allows maturing oocytes to enter interphase and replicate DNA just after meiosis I. Moreover, we demonstrate that during normal maturation cdc2 kinase undergoes precocious inactivation in meiosis I and then premature reactivation before meiosis II; importantly, this premature cdc2 reactivation absolutely requires Mos function and its direct inhibition by a dominant-negative cdc2 mutant also results in nuclear reformation and DNA replication immediately after meiosis I. These findings indicate that suppression of DNA replication during meiotic divisions in Xenopus oocytes is accomplished by the Mos-mediated premature reactivation of cdc2 kinase. We suggest that these mechanisms for suppressing DNA replication may be specific for meiosis in animal oocytes, and that the ultimate biological function, including the well known cytostatic factor activity, of Mos during meiotic maturation may be to prevent undesirable DNA replication or parthenogenetic activation before fertilization.

Animals↗
PubMed1994

A zinc finger protein controls the onset of premeiotic DNA synthesis of fission yeast in a Mei2-independent cascade.

In the fission yeast Schizosaccharomyces pombe, meiosis is initiated by the action of Mei2 in a complex cascade activated following conjugation. We have isolated a new gene named rep1+ that is required for the initiation of premeiotic DNA synthesis. rep1+ encodes a 53 kDa protein with one zinc finger motif that is essential for function, and effectively rescues a null mutant of the res1+ gene but only partially a temperature-sensitive mutant of the cdc10+ gene, both of which are required for the onset of mitotic, as well as premeiotic, S phase. Deletion of rep1+ has no apparent effects on the mitotic cell cycle or conjugation, but blocks the initiation of premeiotic DNA synthesis. However, this defect is partially suppressed when rapidly growing cells are induced to conjugate, indicating that the rep1+ function is at least partly substituted by those of the genes controlling the 'start' of the mitotic cell cycle. The rep1 null mutant fails to induce the res2+ gene, a newly identified res1+ homolog cooperating with Cdc10 and acting for the onset of mitotic and premeiotic DNA synthesis, as well as for meiotic division. The rep1+ gene itself is induced moderately during nitrogen starvation but highly during conjugation, and this induction is dependent on both ste11+ and mating pheromones but independent of mei2+. Thus, rep1+ controls the initiation of premeiotic DNA synthesis via induction and/or activation of Res2 and some other essential factors in a cascade independent of Mei2.

Amino Acid Sequence↗
PubMed1994

A role of calcyclin, a Ca(2+)-binding protein, on the Ca(2+)-dependent insulin release from the pancreatic beta cell.

Exocytosis is an important example of cell activation. Ca2+ and calcium-binding proteins are considered to modulate signal transduction in exocytosis. We examined the role of calcyclin, calcium-binding protein, in the stimulus-secretion coupling in pancreatic beta cells. The presence of calcyclin in these cells was demonstrated immunologically. We permeabilized rat pancreatic islets with streptolysin-O and examined the effects of calcyclin on insulin release. The Ca(2+)-stimulated insulin release was enhanced by calcyclin, in a dose-dependent manner, whereas this calcium-binding protein had no effect on insulin release from islets in low Ca2+ buffer or from the islets not subjected to the streptolysin-O treatment. Calgizzarin, another member of the S-100 protein family, had no apparent effect on the Ca(2+)-stimulated secretion under parallel conditions. An anticalcyclin antibody suppressed the increase in insulin release induced by calcyclin. We propose that calcyclin may be involved in signal transduction of the Ca(2+)-induced release of insulin.

Animals↗
PubMed1994

Heparin-binding domain of bovid herpesvirus 1 glycoprotein gIII.

Bovid herpesvirus 1 (BHV-1) glycoprotein gIII functions as a major virus attachment protein through binding to a heparin-like moiety on the host cells. To identify the functional domain, a panel of gIII deletion mutants was constructed, expressed in COS-7 cells, and examined for heparin-binding activity. Mutants with deletion of amino acid residues 103-173 and 324-443 bound to heparin as well as full-length gIII, whereas a mutant with residues 172-337 deleted showed no binding to heparin. In another mutant, with residues 172-211 deleted, the activity was reduced by one-third. These data suggest that the amino acid sequence between residues 172 and 323 contains the functional domain of BHV-1 gIII for heparin-binding and that especially the sequence between residues 212-323 includes a critical site for the activity.

Amino Acid Sequence↗
PubMed1994

Biosynthesis of mucin derived from a 60-kDa precursor protein in the human stomach.

We studied the biosynthesis of mucin in the human stomach using an anti-mucin core peptide monoclonal antibody, 3G12. Human stomach mucosa was labeled with [35S]methionine, and chased for 3 h. An approximately 60-kDa subunit of human gastric mucin precursor protein was detected in the intracellular product. Under nonreducing conditions, dimer, trimer, and tetramer mucin precursor protein (120, 180, 240 kDa) were detected. Treatment with tunicamycin or endo-beta-N-acetylglucosaminidase H had no effect on the 60-kDa subunit and its oligomers. Extracellular products contained only the high molecular weight mucin, and the secretion was not affected by tunicamycin. By treatment with monensin or brefeldin A, the mature mucin was not secreted extracellularly. These findings suggested that a 60-kDa subunit of the mucin precursor protein was biosynthesized into mature mucin after oligomerization to tetramers, and that neither the oligomerization nor the intracellular transport of the mucin in the human stomach was associated with N-glycosylation.

Antibodies, Monoclonal↗
PubMed1994

T cell cytotoxicity of autologous and allogeneic lymphocytes in a patient with Crohn's disease.

We report a 27-year-old male with Crohn's disease (CD) of the small and large intestine, whose peripheral blood lymphocytes (PBL) showed increased cell-mediated cytotoxicity (CTL). Autologous and allogeneic effector cells from PBL and intestinal lymph nodes (LN) were isolated on a Ficoll-Hypaque gradient. Colonic cells were prepared as the target and were incubated for 6h with effector cells, after being labeled with Na(2)51CrO4. The CTL activity [effector/target (E/T) ratio, 100:1] of PBL for autologous targets was increased by 38% compared with that in normal subjects (< 10%), while that shown by LN was not increased (14%). The CTL activity of allogeneic PBL prepared from three of four other CD patients was also increased. Anti-major histocompatibility (MHC) class I and II and CD4 and CD8 monoclonal antibodies (50 micrograms/ml) significantly inhibited CTL activity. Complement-mediated depletion of CD2+ cells significantly reduced CTL activity. These results suggest that MHC-restricted CTL may play a role in mucosal damage in some patients with Crohn's disease.

Adult↗
PubMed1994

Effects of carbamylcholine chloride on human antral gastrin mRNA levels.

The effects of the muscarinic receptor agonist, carbamylcholine chloride (carbachol), on gastrin release and gastrin mRNA levels in human antral mucosa (n = 15) were determined. During a-2-h incubation period, carbachol (10(-6)-10(-4) M) decreased gastrin mRNA levels to 71 +/- 8% (10(-6) M), 40 +/- 8% (10(-5) M), and 33 +/- 5% (10(-4) M) of control levels. Carbachol (10(-5) M) decreased intracellular gastrin (from 1634 +/- 103 to 1272 +/- 126 pg/mg tissue protein), while it increased gastrin release into the medium (from 609 +/- 48 to 918 +/- 68 pg/ml per mg tissue protein). After 6- and 9-h culture, carbachol gradually increased gastrin mRNA levels, by 96 +/- 12% and 126 +/- 23%, respectively. Atropine sulfate (10(-5) M) completely inhibited the carbachol-induced changes. Cycloheximide markedly decreased tissue gastrin concentration, but increased gastrin mRNA levels, whereas it had no effects on gastrin release. These findings suggested that carbachol may have a time-related biphasic action on human antral gastrin biosynthesis.

Adult↗
PubMed1994

Biosynthesis and secretion of mucin-related products in Hs746T gastric cancer cells.

We have previously studied the biosynthesis and secretion of mucin in the normal human stomach and reported that the tetramer of the 60-kDa subunit of mucin core protein was synthesized and highly glycosylated, and that only high molecular weight mucin was secreted. In this study, we investigated the mucin-related products of a gastric cancer cell line (Hs746T). Analysis of intracellular and extracellular products immunoprecipitated with an anti-apomucin monoclonal antibody revealed that a 110-kDa protein, the dimer of the 55-kDa subunit, was synthesized and secreted. Tunicamycin treatment inhibited the secretion of the 110-kDa protein. These findings suggest that N-glycosylation may be involved in the secretory mechanism of the mucin-related product.

Adenocarcinoma↗