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Biomedical subjects

H Takamura

Publications and source records attributed to H Takamura.

At least 73 records · Page 4Linked to original sources
PubMed1986

Search for possible antitumor promoters by inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced Epstein-Barr virus activation; ursolic acid and oleanolic acid from an anti-inflammatory Chinese medicinal plant, Glechoma hederaceae L.

From an anti-inflammatory Chinese medicinal plant, Glechoma hederaceae L., two triterpene carboxylic acids, ursolic acid (UA) and oleanolic acid (OA) have been isolated as inhibitors of 12-O-tetradecanoylphorbol-13-acetate (TPA) induced Epstein-Barr virus (EBV) activation in Raji cells. Both acids significantly inhibited the activation at a 1000-fold molar ratio to TPA, and also teleocidin B-4. The dose responses of the acids were very similar to those of the antitumor promoters, retinoic acid (RA) and glycyrrhetinic acid (GA). However, a characteristic property that UA and OA possess, far higher cell viability to the Raji cells than RA to the Raji cells, has been pointed out. Furthermore, enhancement of the inhibitory activity was found in 3-keto derivatives of UA and OA, while either loss of oxygen functionality at C-3 position of UA or oxidation at C-3 of GA led to reduction of the activity. Binding assay suggested that the inhibitory activity should be exhibited by some event caused after binding of TPA to the receptor in the cells.

Biological Assay↗
PubMed1986

Dissociation of Ca2+ mobilization from breakdown of phosphatidylinositol 4,5-bisphosphate in activated human platelets.

The early breakdown of phosphatidylinositol 4,5-bisphosphate in human platelets stimulated by a threshold concentration of either collagen or thrombin was inhibited by 5 mM NaF through its inhibition of phospholipase C activity. However, 5 mM NaF did not inhibit Ca2+ mobilization due to the stimuli from internal stores, but it did inhibit the influx of extracellular Ca2+ through its suppression of thromboxane A2 formation.

Blood Platelets↗
PubMed1985

Phosphoinositide breakdown as an indirect link between stimulation and aggregation of rat platelets by thrombin and collagen.

When washed rat platelets (1.5 x 10(9)/ml) were stimulated by a threshold concentration of thrombin (0.3 unit/ml) or collagen (10 micrograms/ml), a lag period of about 10 or 30 s, respectively, was seen before the start of aggregation. During the lag period, [32P]phosphatidylinositol 4,5-bisphosphate was degraded as the earliest event within 5-10 s of addition of the stimulus. However, though the extent of phosphatidylinositol 4,5-bisphosphate degradation within 10 s of addition of collagen was greater than that within 20 s of addition of thrombin (0.3 unit/ml), a lag of about 20 s remained before the initiation of aggregation by collagen. This casts doubt on the hypothesis that the stimulus-dependent phosphatidylinositol 4,5-bisphosphate breakdown induces the aggregation of platelets. Phosphatidylinositol labeled with 32Pi or [1-14C]arachidonic acid was scarcely degraded during the lag period. As aggregation proceeded, [14C-arachidonic acid]phosphatidylinositol was degraded with generation of diacylglycerol, phosphatidic acid, arachidonic acid and its metabolites. The maximum aggregation by collagen of rat platelets in which arachidonic acid of phospholipids was replaced in vivo with eicosapentaenoic acid was reduced, but that by thrombin was not, though reduction of thromboxane A2 generation was caused by both stimuli. Indomethacin also fully inhibited the aggregation induced by collagen, but not that induced by thrombin. Hence, thromboxane A2 is required for full aggregation by collagen, but not that by thrombin. These results indicate that thrombin-induced phosphoinositide metabolism may proceed independently of aggregation.

Animals↗
PubMed1985

A sensitive method for quantitative analysis of phospholipid molecular species by high-performance liquid chromatography.

A simple and sensitive method was developed for quantitative analysis of phospholipid molecular species. Diacylglycerols were prepared from phospholipids by phospholipase C treatment and converted to the corresponding dinitrobenzoyl derivatives, which could be sensitively detected at 254 nm. The derivatives of 21 molecular species were resolved by high-performance liquid chromatography with an octadecylsilyl reversed-phase column. All the derivatives had the same peak area per mol, and peak areas were proportional to the amounts of the derivatives. Quantification was carried out at the picomole level.

Chromatography, High Pressure Liquid↗
PubMed1984

Congenital anaplastic ependymoma: a case report of familial glioma.

A congenital anaplastic infratentorial ependymoma, occurring in a female infant whose sister also died of brain tumor, is described. The tumor, located in the cerebellum and the fourth ventricle, is characterized by predominantly undifferentiated neuroepithelial cells associated with numerous mitoses, and partially of the cells demonstrating differentiation into ependymal cells and astrocytes. Of special interest is the fact that the elder sister of the patient had also died of a congenital glioma located in the cerebellum and the fourth ventricle, which leads to the discussion about the influences of genetic factors in the development of the familial gliomas as well as about the histogenesis of the tumor examined.

Brain Neoplasms↗
PubMed1980

Congenital cerebellar neuroepithelial tumor with multiple divergent differentiations.

A case of congenital cerebellar tumor is reported. The tumor is composed of a few incomplete tubular structures analogous to the neural tube, and of neuroblastic, mature ganglionic, astrocytic, ependymal and undetermined neuroepithelial cells. A tentative diagnosis of congenital cerebellar neuroepithelial tumor with multiple divergent differentiations is made: the histogenesis is discussed. From a histogenetic point of view this tumor is given the provisional name of matrix cell tumor.

Autopsy↗
PubMed1976

[Nasopharyngeal extension of a large chromophobe adenoma of the pituitary (author's transl)].

It is not common to have experienced the nasopharyngeal extension of pituitary adenomas. Recently we have experienced such a case. A man, aged 18, height 168 cm, weight 66 kg, who admitted to the hospital with the complaints of headache, left nasal obstruction, loss of visual acuity and defect of his temporal fields. On examination of both fundi there was primary optic atrophy. At this time large tumor could be seen in the nasopharyngeal cavity. Plain X-ray showed that the pituitary fossa was definitely enlarged and that there was considerable destruction of the sella and the clivus. Definite soft tissue mass could be visualised clearly by tomography. Via transoral and transsphenoidal approach, total removal of the nasopharyngeal tumor and intracapsulary subtotal resection of the tumor were performed. Microscopical examination established the diagnosis of chromophobe adenoma. On postoperative examination of hypothalamopituitary function he had no responces to insulin hypoglycemia and arginine infusion in growth hormone. 60Co irradiation, totally 6,000 rad, was given. Two years postoperatively he showed fairly good deal of improvement of his visual field defect. There was no serious complaints other than visual impairment on the left eye.

Adenoma, Chromophobe↗
PubMed1975

[The protrusion of thoracic intervertebral disc-thoracic spondylosis (author's transl)].

The protrusion of cervical intervertebral discs was divided into three pathological entities by Spurling; soft disc, hard disc and spondylosis. We applied these concept to the dorsal intervertebral disc disease and treated two cases of thoracic spondylosis. Case 1. A 41-year-old male entered the hospital because of the gradual progression of weakness of both legs of two months' duration. Since ten days before admission he had not had an errection and had not been to able to walk and micturate. He also complained of paresthesia radiating down the abdomen into both legs. There were no visceral complaints. Neurological examination revealed severe weakness of both legs with bilateral impairment of deep sensations and hypalgesia up to the level of T6. Reflexes in both legs were hyperactive with sustained clonus. Plantar responses were extensor bilaterally. Though plain X-rays showed no changes, tomography revealed a calcified intervertebral spur formation at the T5-6 interspace. A myelogram showed a complete block of the contrast medium at the level of the upper part of T6. The patient underwent a complete laminectomy from T3 through T6 and extradural anterior decompression with the removal of the calcified disc at the T5-6 interspace using an air drill. Postoperatively, he demonstrated an immediate improvement in sensation and a gradual recovery in motor power. At his follow-up examination 14 months after surgery he could walk without assistance. Case 2. A 47-year-old dwarfish woman (130 cm) with a low back pain and difficulty in walking for a few years duration was admitted. A few months before admission she felt pain at her left lateral abdomen. There was weakness of both legs, greater in the left. Reflexes in her left lower extremity were hyperactive with sustained clonus. Plantar responces were flexor bilaterally. Palin X-rays showed scoliosis of thoracic spine with the top at T7 level and calcified intervertebral masses at T10-11, T11-12 and T12-L1, extending into the canal that were confirmed more clearly by tomography. Myelography by a cisternal puncture disclosed a complete block at the level of T10. The patient underwent total laminectomy of T9 through L2 and extradural anterior decompression with the removal of calcified discs. At her follow-up examination 12 months after surgery she could walk for herself with some residual neurological signs, minimal weakness in the right leg and hypesthesia up to the level of T12 in the left. We have discussed the incidental, related diagnostic and operative problems of this disease.

Adult↗