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Biomedical subjects

O Ohara

Publications and source records attributed to O Ohara.

At least 73 records · Page 4Linked to original sources
PubMed1995

Vascular smooth muscle cell-derived, Gla-containing growth-potentiating factor for Ca(2+)-mobilizing growth factors.

Proliferation of vascular smooth muscle cells (VSMC) is triggered by two types of growth factors. One activates tyrosine kinase-type receptors and the other activates G-protein-coupled receptors. We found that a conditioned medium of rat VSMC contained a growth-potentiating activity for the latter type of growth factor, and we purified a 70-kDa growth-potentiating factor (GPF) from the conditioned medium. Analyses of GPF and its cDNA revealed GPF to be a gamma-carboxyglutamic acid-containing protein encoded by a growth arrest-specific gene, gas6, which related to protein S. GPF specifically potentiated cell proliferation mediated by Ca(2+)-mobilizing receptors. The presence of a specific binding site suggests that the effect of GPF is mediated by a receptor. Thus, GPF may be a new type of extracellular factor regulating VSMC proliferation.

Amino Acid Sequence↗
PubMed1995

Pancreatic-type phospholipase A2 activates prostaglandin E2 production in rat mesangial cells by receptor binding reaction.

Our earlier studies have shown that mammalian pancreatic group I phospholipase A2 (PLA2-I) has its specific receptor (PLA2 receptor) on a wide range of mammalian cells and that the receptor-binding capability of PLA2-I is a property of this molecule separable from its enzymatic activity. To clarify whether PLA2 activity is required for eliciting a biological response via the receptor or not, we examined the enzymatic activity of PLA2-I/PLA2 receptor complex and the inducibility of prostaglandin (PG) E2 production in rat mesangial cells by mutant PLA2s-I. Using a recombinant soluble PLA2 receptor, we first found that PLA2-I could not hydrolyze a phospholipid substrate when complexed with the receptor. In the next experiment using various mutant porcine PLA2s-I, we found that PGE2 production in rat mesangial cells could be induced by a mutant PLA2-I which retained the receptor-binding activity but had almost completely lost its enzymatic activity. These findings indicate that the enzyme action of PLA2-I is not required for a PLA2-I-induced biological response, i.e., the augmentation of PGE2 production in rat mesangial cells.

Animals↗
PubMed1995

Effects of brain-derived neurotrophic factor on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism in monkeys.

The effects of intrathecal infusion of brain-derived neurotrophic factor (BDNF) were examined in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonian model in monkeys. Nine Japanese monkeys were divided randomly into three groups, an untreated control (n = 3), a BDNF group (n = 3), and a non-BDNF group (n = 3). Animals in the BDNF group received continuous intrathecal infusion of 10 ml of cell culture medium containing 10 micrograms of BDNF protein; the non-BDNF group received intrathecal infusion of the same culture medium without BDNF. To induce parkinsonian syndromes, a total of 1 mg/kg 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine was administered intravenously to each monkey in both the BDNF and non-BDNF groups. The neurological signs in the monkeys were monitored for 2 weeks and were scored according to the monkey parkinsonism rating scale; histological changes in the substantia nigra were evaluated after the 2-week observation period. The BDNF-treated animals remained asymptomatic during the 1st week and showed mild parkinsonism during the 2nd week, whereas the non-BDNF group showed typical parkinsonian syndrome during the 1st week, with deterioration in the 2nd week. Histological damage in the substantia nigra correlated well with the clinical features. Severe neuronal cell loss in the substantia nigra was observed in animals with severe parkinsonism (those in the non-BDNF group), whereas significantly less damage was observed in this region in the BDNF group.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1995

A novel RING-H2 motif protein downregulated by axotomy: its characteristic localization at the postsynaptic density of axosomatic synapse.

Axonal injury and its repair are common and basic neuropathological processes in the CNS, and are composed of a complex of events in a molecular term. In order to get a comprehensive understanding of these processes, we isolated several known and unknown genes which were up-or downregulated in the facial nucleus after transection of the facial nerve by a subtractive/differential screening. Among them, we focus on one downregulated gene, named Neurodap1, because this gene encodes a novel protein carrying the RING-H2 sequence motif categorized in the zinc finger family. Immunoelectron microscopic analysis revealed that the protein encoded by Neurodap1, Neurodap1, was distributed mainly on the cytoplasmic side of the membranes constituting endoplasmic reticulum and Golgi apparatus, supporting the notion of a previously postulated function of RING-H2 motif proteins, that is, involvement in the protein sorting machinery. More interestingly, Neurodap1 was also bound to the postsynaptic density (PSD) region of axosomatic synapses. This fact suggests that Neurodap1 is associated with a specific system sorting proteins to PSD. Therefore, Neurodap1, a newly identified protein as an axotomy-suppressed gene product, might play a significant role in synaptic communication and plasticity through the control of the formation of PSD for maintaining vital functions of nerve cells.

Amino Acid Sequence↗
PubMed1994

Structural comparison of phospholipase-A2-binding regions in phospholipase-A2 receptors from various mammals.

We determined the nucleotide sequence of a mouse cDNA encoding the receptor for pancreatic group I phospholipase A2 (PLA2-I). Interspecies structural comparison of the mouse receptor with bovine PLA2-I receptor, whose structure had been clarified, revealed that the fourth carbohydrate-recognition domain (CRD)-like domain (CRD-like 4) was the most conserved among the domains in the PLA2-I receptor, suggesting the functional importance of CRD-like 4. A transient expression experiment with a truncated form of the receptor consisting of three CRD-like domains, from the third to the fifth, demonstrated that the PLA2-I-binding site of the receptor is constituted from these three CRD-like domains, supporting the functional indispensability of CRD-like 4 in the receptor. Since the PLA2-I-binding region was thus assigned to be CRD-like domains 3-5, we further analyzed the structures of the PLA2-I-binding regions in the PLA2-I receptors from the rat, rabbit and human. Furthermore, the obtained PLA2-I receptor cDNA fragments from these animals made it possible to examine the tissue expression patterns of this receptor in various mammals. The results, together with the results of the genomic structural analysis of this gene, indicated that a PLA2 receptor recently characterized by Lambeau et al. [Lambeau, G., Ancian, P., Barhanin, J. & Lazdunski, M. (1994) J. Biol. Chem. 269, 1575-1578] is a rabbit counterpart of the PLA2-I receptor although these two PLA2 receptors have distinctive PLA2-binding specificities.

Amino Acid Sequence↗
PubMed1994

Molecular cloning of pancreatic group I phospholipase A2 receptor.

We have recently reported that mammalian pancreatic group I phospholipase A2 (PLA2-I) has its specific receptor (PLA2 receptor) on a variety of mammalian cells and that various biological responses are elicited by PLA2-I via this receptor. In this study, we cloned cDNAs encoding a protein corresponding to the bovine PLA2 receptor purified from the corpora lutea on the basis of its partial amino acid sequences. The identity of a protein encoded by the cloned cDNA with the bovine PLA2 receptor was verified by a transient expression experiment using COS-7 cells. Interestingly, the deduced primary structure of the PLA2 receptor (1,463 amino acid residues) exhibits a close relatedness throughout the molecule to that of the macrophage mannose receptor, a unique member of Ca(2+)-dependent (C-type) animal lectin family, in spite of their functional diversity. Based on this sequence similarity between these two receptors, the domain organization of the PLA2 receptor could be tentatively assigned as follows; 10 extracellular domains including 8 tandem repeats homologous to C-type carbohydrate-recognition domains (CRDs) and a single transmembrane region followed by a short cytoplasmic tail. The results of transient expression experiments for mutant PLA2 receptors supported this assignment and furthermore suggested the region responsible for PLA2-I binding corresponds to CRDs in the mannose receptor.

Amino Acid Sequence↗
PubMed1994

Pancreatic-type phospholipase A2 induces group II phospholipase A2 expression and prostaglandin biosynthesis in rat mesangial cells.

The effect of pancreatic group I phospholipase A2 (PLA2-I) on receptor-mediated expression of arthritic group II phospholipase A2 (PLA2-II) and its correlation with prostaglandin E2 (PGE2) synthesis were examined in cultured rat mesangial cells. Scatchard analysis using 125I-PLA2-I revealed the existence of a single class of specific binding sites for PLA2-I in rat mesangial cells with an equilibrium dissociation constant (Kd) of 1.6 nM and a maximum binding capacity of 10.1 fmol/10(6) cells. The mammalian mature type of PLA2-I specifically recognized this binding site, whereas its inactive zymogen and mammalian PLA2-II showed much lower affinities. PLA2-I markedly increased PLA2-II mRNA levels as well as PLA2-II secretion from the cells in a time- and dose-dependent manner that was closely correlated with PGE2 production. Both PLA2-II expression and PGE2 synthesis were completely suppressed by pretreatment of the cells with actinomycin D, cycloheximide, or dexamethasone. These results strongly suggest that there may be crosstalk between PLA2-I and PLA2-II via the specific PLA2-I receptor that elicits PGE2 synthesis.

Animals↗
PubMed1994

Gastrocolic fistula originating from transverse colon cancer: report of a case and review of the Japanese literature.

A 72-year-old woman was admitted to our hospital complaining of loss of weight, general fatigue, and upper abdominal pain. Barium studies suggested that a fistula was present between the proximal transverse colon and the stomach which originated from a carcinoma of the colon. A plain computed tomography (CT) scan confirmed the presence of a gastrocolic fistula. A two-thirds distal gastrectomy and right hemicolectomy with a resection of a bulky tumor in the mesocolon were performed en bloc. Histological examination revealed a well-differentiated adenocarcinoma of the transverse colon which was involved with the wall of the stomach. We were able to obtain information on 14 previous cases of gastrocolic fistula originating from transverse colon cancer in the Japanese literature, including the present case. The most common symptom was abdominal pain (64%). A preoperative diagnosis of fistula was confirmed in 10 of the 11 cases examined by barium studies. A plain CT and a CT scan after the barium studies may also be helpful in detecting fistula formation. A fistula between the carcinoma of the middle or distal transverse colon and the stomach was found in 13 of 14 cases, but not in our case. Only one case lived longer than 9 years, even though a surgical resection was possible in 9 of 11 cases.

Adenocarcinoma↗
PubMed1994

Distinctive four promoters collectively direct expression of brain-derived neurotrophic factor gene.

In order to get a deeper insight into comprehensive understanding of gene regulation of brain-derived neurotrophic factor (BDNF), we characterized the transcriptional apparatus of this gene on the basis of the genomic structure. The results in this study revealed that there are at least four distinctive promoters in the BDNF gene; two of them are neuron-specific and the rest are active in some non-neuronal tissues as well as neuronal ones. Although the analyses of the promoter usage pattern clarified many characteristic features in controlling these promoter activities, the most notable finding was that administration of kainic acid resulted in great activation of two out of the four promoters in hippocampal neurons in a regionally different manner and thus indicated the presence of two distinct signal transduction pathways for kainate-induced activation of BDNF gene expression in neurons. The analysis of BDNF gene expression in terms of the promoter usage pattern would provide a new and important insight into understanding a molecular control mechanism of this gene expression.

Animals↗
PubMed1994

A novel method for generating nested deletions using the in vitro bacteriophage T3 DNA packaging system.

To sequence a DNA segment inserted into a cosmid vector under the directed sequencing strategy, we established a simple and rapid method for generating nested deletions which uses the in vitro packaging system of bacteriophage T3 DNA. The principle is based on the previous finding that this system can translocate any linear double-stranded DNA up to 40 kb into the phage capsid in a time-dependent manner and the encapsulated DNA becomes DNase-resistant. For this purpose, we constructed a cosmid vector that carries two different antibiotic selection markers at both sides of the multiple cloning site, and after insertion of a DNA segment, the clone was linearized by lambda-terminase at the cos site. After the packaging reaction in vitro followed by DNase treatment, the encapsulated DNA was introduced into Escherichia coli cells to give clones with unidirectional deletions by differential antibiotic selection. Restriction and sequence analyses of deletion clones demonstrated that an ordered set of clones with nested deletions, ranging from less than 1 kb to 25 kb, was created from either the end of the DNA segment. Thus, nested deletion clones that cover the entire region of a approximately 40-kb cosmid insert can be obtained by a single packaging reaction, and its restriction map can be simultaneously obtained.

Bacteriophage T3↗
PubMed1994

The role of brain-derived neurotrophic factor in transient forebrain ischemia in the rat brain.

Brain-derived neurotrophic factor (BDNF) may play a role in the pathophysiology of neuronal cell death after cerebral ischemia. We investigated alterations in BDNF gene expression and the effect of BDNF on neuronal death after transient forebrain ischemia in the rat brain. Transient forebrain ischemia was induced by occlusion of the bilateral common carotid arteries and by producing systemic hypotension for 8 minutes. The alterations in the BDNF messenger ribonucleic acid content in the hippocampus and the cerebral cortex were examined by Northern blot analysis, using a phosphorus-32-labeled mouse BDNF complementary deoxyribonucleic acid probe. Recombinant Chinese hamster ovary cells with BDNF-secreting capacity were established by expression vector transfection with BDNF complementary deoxyribonucleic acid. The effect of BDNF on neuronal death in the hippocampal CA1 region after ischemia was then examined by using a continuous intraventricular infusion of 200 microliters of normal (Group II, n = 6) or 30-times concentrated recombinant Chinese hamster ovary cell culture medium containing BDNF (Group IV, n = 6). Normal (Group I, n = 6) or 30-times concentrated (Group III, n = 6) Chinese hamster ovary cell culture medium, not including BDNF complementary deoxyribonucleic acid, was infused into the same ischemic brains, which served as controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Brain-derived neurotrophic factor pretreatment exerts a partially protective effect against glutamate-induced neurotoxicity in cultured rat cortical neurons.

The effect of recombinant brain-derived neurotrophic factor (BDNF) on cultured rat cortical neurons was examined. Brief exposure of cortical neurons to glutamate followed by incubation with glutamate-free medium reduced cell viability by 60-70% when compared with the control value. Simultaneous addition of recombinant BDNF to rat cortical cultures with glutamate did not affect this reduction of cell viability. However, 24 h pretreatment of rat cortical cultures with recombinant BDNF resulted in a significant reduction of glutamate-induced neuronal damage. These findings suggest that BDNF can protect cortical neurons against glutamate-induced neurotoxicity.

Animals↗
PubMed1993

Receptor-binding capability of pancreatic phospholipase A2 is separable from its enzymatic activity.

Mammalian pancreatic phospholipase A2 (PLA2-I) has its specific receptor through which PLA2-I induces a variety of biological responses. In this study, a fundamental relationship between the enzymatic and the receptor-binding activities of PLA2-I was investigated. The specific binding of PLA2-I to the receptor was found to be independent of Ca2+ which is requisite for the PLA2 activity. On the basis of this observation, we designed and produced mutant PLA2-Is without Ca(2+)-binding abilities in order to demonstrate that the structural requirement for the enzymatic activity of PLA2-I is not identical with that for its receptor-binding reaction. These mutant PLA2-Is lost almost all enzymatic activity through a disturbance at the Ca(2+)-binding site, as expected, but still retained a substantial affinity to the receptor, allowing us to conclude that the receptor-binding reaction of PLA2-I is separable from its catalytic action.

Animals↗
PubMed1993

A case of intracystic carcinoma of the breast: the importance of measuring carcinoembryonic antigen in aspirated cystic fluid.

We report a case of intracystic carcinoma of the breast in which a correct preoperative diagnosis was achieved on the basis of an increased level of carcinoembryonic antigen (CEA) in the aspirated cystic fluid. A 62-year-old woman was admitted with a 10 x 10 cm painful mass occupying the right breast. Ultrasonography revealed a cystic lesion with papillary projections arising from the cyst wall. Cytological examinations showed no malignant cells in the hemorrhagic aspirated fluid. However, the CEA level in the fluid was 5.5 times higher than the serum CEA level using a murine anti-CEA monoclonal antibody. The high level of CEA led to the preoperative diagnosis of intracystic carcinoma. Histological examinations confirmed the diagnosis of intracystic carcinoma after a modified radical mastectomy. Immunohistochemical staining by an anti-CEA monoclonal antibody elicited a strong positivity with diffuse intracytoplasmic distribution in the carcinoma cells, although heterogeneity of staining was observed. It is suggested that the measurement of the CEA value by anti-CEA monoclonal antibody in the aspirated fluid is easy, safe, and helpful for the definitive diagnosis of intracystic carcinoma of the breast.

Breast Neoplasms↗