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Biomedical subjects

F Yamada

Publications and source records attributed to F Yamada.

At least 19 recordsLinked to original sources
PubMed1995

Cytoskeletal reorganization of human platelets induced by the protein phosphatase 1/2 A inhibitors okadaic acid and calyculin A.

Okadaic acid (OA) and calyculin A (CLA), which are potent and specific inhibitors of serine/threonine protein phosphatases type 1 and 2A, have been shown to induce drastic changes in platelet morphology. The aim of this study was to analyse the molecular mechanisms of OA- or CLA-induced cytoskeletal reorganization, with a specific focus on microtubules and actin filaments. Confocal fluorescence microscopy revealed that OA or CLA altered the distribution of microtubules from marginal band arrangements to homogeneous patterns, consistent with the transmission-electron-microscopic finding that microtubules were fragmented and redistributed into pseudopod-like processes. In thrombin-activated platelets, OA or CLA induced extremely long pseudopods containing an array of microtubules and actin filaments, and a condensed mass of actin filaments in the centre of platelets. OA or CLA induced the constriction of actin filaments without an increase in filamentous (F)-actin, and also rather significantly inhibited actin polymerization in thrombin-activated platelets. Furthermore, neither OA or CLA enhanced phosphorylation of myosin light chain (MLC). By immunoprecipitation of platelet lysate with anti-alpha-tubulin antibody, a 90 kDa protein was co-precipitated with tubulin and was predominantly phosphorylated in the presence of OA. As the time-dependent phosphorylation of 90 kDa protein correlated well with the reorganization of microtubules, these data suggest that phosphorylation and dephosphorylation of this protein might play a role in the regulation of microtubule organization. These findings indicate that OA or CLA induces reorganization of microtubules and actin filaments via the phosphorylation of a microtubule-associated 90 kDa protein and an MLC-phosphorylation-independent mechanism. mechanism.

Actins↗
PubMed1995

[Study of hepatic arterial infusion chemotherapy for prophylaxis of liver metastases of colorectal cancer after hepatic resection].

We examined the significance of hepatic arterial infusion chemotherapy (HAIC) for prophylaxis of liver metastases of colorectal cancer after hepatic resection using an implantable port. Fifty-five patients operated at the hospital from August 1988 to December 1994 were divided into two groups consisting of 23 patients with HAIC group: (HAIC (+)), and 32 patients without HAIC group: (HAIC (-)) retrospectively. The cumulative survival rates and recurrent rates of cancer free in remnant liver of HAIC (+) were improved, compared with HAIC (-). This suggests that HAIC was effective in improving the prognosis and preventing recurrence in remnant liver.

Adult↗
PubMed1995

[Two cases of catheter tip dislocation to the duodenal bulb: a rare complication of hepatic arterial infusion chemotherapy].

Case 1: A 63-year-old woman underwent transverse colectomy and hepatectomy for colonic cancer and liver metastasis. A hepatic arterial infusion port (HAIP) was implanted. Continuous infusion of 5-FU (total amount, 7,500 mg) caused a hemorrhagic duodenal ulcer 15 months after. Follow-up endoscopy revealed the catheter tip was in the duodenal bulb. Case 2: A 62-year-old man underwent abdominoperineal resection for rectal cancer. Repeated hepatectomy for liver metastases was performed at 3 and 5 years after the first operation. HAIP was implanted at the last operation, but was not available at all due to the wound infection. The port was removed, but the catheter remained. Three years after, the catheter tip was found in the duodenal bulb by endoscopy.

Catheters, Indwelling↗
PubMed1995

[Post operative mediastinitis: the experience of two cases after graft replacement of the ascending aorta].

A mediastinitis after a graft replacement of the ascending aorta is serious complication and sometimes could be lethal. We have experienced two cases of such a condition, recently. In both cases, the debridement of the mediastinum and omental transposition were performed. Case 1 had a recurrent mediastinitis due to residual dead space infection, but was cured by a percutaneous drainage and a continuous irrigation. In case 2, the omentum was carefully positioned to occupy the dead space around the graft, because of the experience of the first case and gave a good result. We believe that omental transposition is an effective treatment for the postoperative mediastinitis.

Adult↗
PubMed1994

Discrepancy between PNMT presence and relative lack of adrenaline production in extra-adrenal pheochromocytoma.

Among catecholamine synthesizing enzymes, phenylethanolamine-N-methyltransferase (PNMT) exists only in adrenal and extra-adrenal pheochromocytoma has been believed not to produce adrenaline. However, adrenaline production is clinically active in some extra-adrenal cases. To investigate this controversy, the localization of catecholamine synthesizing enzymes was studied by immunohistochemical staining in extra-adrenal and adrenal cases. The results showed that PNMT was expressed not only in many cases of adrenal pheochromocytoma, but also in extra-adrenal pheochromocytoma. It is suspected that little adrenaline production in extra-adrenal cases is attributable to a lack of a good environment for the activation of PNMT by a high concentration of glucocorticoids.

Adrenal Gland Neoplasms↗
PubMed1994

Mixed germ cell tumor of the basal ganglia: a case report.

A case of mixed germ cell tumor (germinoma and immature teratoma) of right cranial basal ganglia is presented. We followed the natural course for 8 months, and the change in his clinical, radiologic, and endocrinologic features was remarkable.

Adolescent↗
PubMed1994

[Biological characters of enterohemorrhagic Escherichia coli isolates from diarrhea patients in Saitama (1990-1992)].

A total of 16 strains of Enterohemorrhagic Escherichia coli (EHEC) isolated from diarrea patients in Saitama from 1990 to 1992 were tested for their serotype, verotoxin production, biochemical characteristics, antibiotics sensitivity and plasmid profiles. By serotype analysis, 14 strains from two outbreaks and 12 sporadic cases were classified as type O157:H7, one as O111:H-(not motility) and one as O128:H2. Typing of verotoxin by gene analysis using Polymerase Chain Reaction (PCR) showed that 9 of O157:H7 strains including two cases from outbreaks and O128:H2 have VT1 and VT2 genes, other O157:H7 have the VT2 gene and O111:H-has only the VT1 gene. Biochemical characteristic analysis indicated two strains of O157:H7 type from outbreaks were biotype II and the rest of O157:H7 were biotype I. One of the O157:H7 strain from a sporadic case showed positive for urease production. According to sensitivity tests against antibiotics, out of the O157:H7 group, one strain was resistant against ABPC, one against SM and two strains resistant to SM-TC. For plasmid profiles, all strains had 94 Kb plasmids and several smaller sizes of plasmids. But 5 strains of O157:H7 had 94 Kb plasmid only.

Bacterial Toxins↗
PubMed1994

[The first report of traveler's diarrhea associated with a newly described toxigenic Vibrio cholerae O139 strain in Japan].

A newly described Vibrio cholerae O139 was isolated from a patient who had traveled in India on April 1993. The patient experienced 5 to 6 watery diarrhea per day after he returned to Japan. The isolated strain registered as K111 did not agglutinate with O1-O138 antiserum and agglutinated with O139 antiserum. This strain resembled V. cholerae O1 strain in biochemical characters and had ctx and zot, although was resistant to the vibrio static agent O/129. This is the first report of cholera-like illness by the newly described toxigenic V. cholerae O139 strain in Japan.

Base Sequence↗
PubMed1994

[Cerebral cysticercosis treated with praziquantel--a case report].

We report a patient with cerebral cysticercosis treated with praziquantel. The patient, a 30-year-old man, was admitted to our hospital with a 12-year-history of generalized convulsion. MRI of the brain showed multiple cysts and the largest one in the right frontal lobe measured 3 cm in diameter. The intensity of cyst contents was same as that of the CSF on T1- and T2-weighted images. X-Ray of extremities and blood examinations showed no abnormal findings. The immunological testing for cysticercosis was negative in the serum. An operation was performed for the largest cyst in the right frontal lobe. The cyst was pathologically confirmed as cysticercosis. He was treated with praziquantel 50 mg/kg body weight in 3 divided doses per day with steroid cover for 7 days. The same therapy was repeated at an interval of 14 days. The patient was suffering from headache and scintilating scotoma only for a few days during the therapy. MRI revealed reduction in the size of the cysts in the right occipital lobe but no change in the other cysts. He was given praziquantel 600 mg per day for two months. As a result, the cysts in the right occipital lobe disappeared and the other cysts diminished on MRI.

Adult↗
PubMed1994

[A juvenile onset case of moyamoya disease with intraventricular hemorrhage during pregnancy: case report].

We report a primipara with intracranial bleeding during pregnancy. The patient, a 23-year-old female, had history of cerebral ischemic attack during childhood and was diagnosed as having moyamoya disease at the age of ten. She did not undergo reconstructive vascular surgery but had not suffered from the cerebral ischemic attack in the last ten years. She suddenly lost consciousness in the eighth month of pregnancy and was admitted to our hospital. The brain CT scan revealed right paraventricular hemorrhage with ventricular perforation. After the newborn baby was delivered by cesarean section under spinal anesthesia, an emergency ventricle drainage was performed. The angiography demonstrated the occlusion of the internal carotid arteries at C1 portion with evidence of a moderate basal moyamoya network on both sides. Marked dilatation of the posterior lateral choroidal arteries was also seen on both sides, but no aneurysms were found. We supposed that the source of intracranial hemorrhage was a breakdown of the dilated perforating moyamoya vessels that formed the basal collateral network. We also supposed that the time of onset of intracranial hemorrhage might be related to the hemodynamic and hormonal changes occurring during pregnancy. Appropriate counterplans to pregnancy should be made by females with moyamoya disease, because pregnancy may be risky for them.

Adult↗
PubMed1993

Altered fibronectin-dependent cell adhesion by PDGF accompanies phenotypic modulation of vascular smooth muscle cells.

PDGF promotes growth of smooth muscle cells (SMCs) and induces morphological changes. We investigated the effects of PDGF on cell-matrix adhesion of SMCs. PDGF reorganized integrin distribution as well as actin filament structure. PDGF-treated cells attached more loosely to fibronectin than non-treated cells. Decreased expression of alpha-actin by PDGF was antagonized by coating culture dishes with fibronectin but not with vitronectin and laminin. The inhibition of cell adhesion by GRGDSP oligopeptide and anti-fibronectin receptor antibody led to the reduction in alpha-actin expression. These results suggest that PDGF may modulate phenotype of SMCs by altering fibronectin-integrin interaction.

Actins↗
PubMed1993

Responses of smooth muscle cells to platelet-derived growth factor are inhibited by herbimycin-A tyrosine kinase inhibitor.

Platelet-derived growth factor (PDGF) plays important roles in proliferation of smooth muscle cells (SMCs). PDGF is also known to induce the cytoskeletal reorganization as a chemoattractant. In this communication, we demonstrate that the tyrosine kinase inhibitor herbimycin-A (HM-A) inhibited the effects of PDGF on SMCs in proliferation, phenotypic modulation, and reorganization of F-actin. Another tyrosine kinase inhibitor genistein also inhibited reorganization of F-actin. Since both tyrosine kinase inhibitors reduced PDGF-dependent tyrosine phosphorylation, tyrosine kinase activities may be involved not only in proliferation but also in reorganization of F-actin.

Actins↗
PubMed1993

Epidermoid cysts of the callosal region--three case reports.

Three patients with rare epidermoid cyst in the callosal region are described, two adjacent and one in the corpus callosum. Computed tomography revealed atypical features, i.e. a large, well-defined high-density mass unenhanced postcontrast and a well-defined hypodense mass with marginal calcification in one case each. Such a diffuse high-density mass may be caused by hemorrhage, highly concentrated protein or calcification of keratinized debris within the cyst. Marginal calcification may occur for unknown reasons. The cysts were subtotally removed.

Adult↗
PubMed1992

Diphosphorylation of platelet myosin ex vivo in the initial phase of activation by thrombin.

We prepared anti-platelet 20-kDa myosin light chain (MLC-20) antibody and demonstrated diphosphorylation of MLC-20 in platelets ex vivo in the initial phase of activation by thrombin. Our results are as follows. (1) By Western blotting, using anti-MLC-20 antibody, both mono- and diphosphorylated myosin were seen in the initial phase of aggregation of platelets by thrombin. The peak of the diphosphorylation was later than that of monophosphorylation and the degree of both mono- and diphosphorylation reduced in the process of aggregation. (2) ML-7 (a synthetic inhibitor of MLCK) inhibited both mono- and diphosphorylation of myosin and also blocked aggregation of thrombin-activated platelets. However, H-7 (an inhibitor of protein kinase C) had little effect on either the (di)phosphorylation of myosin or the aggregation of thrombin-activated platelets. (3) Arg-Gly-Asp-Ser (RGDS) peptide, a synthetic anti-adhesive peptide, inhibited aggregation of thrombin-activated platelets in a dose-dependent manner (100-200 microM). However, it had little effect on either mono- or diphosphorylation of myosin in the process of the platelet aggregation stimulated by thrombin. From these results, we conclude that mono- and diphosphorylation of myosin by MLCK play a role in the initial phase of activation of thrombin-stimulated platelets in vivo and that mono- and diphosphorylation of myosin by MLCK precedes the secondary signal mediated by GPIIb/IIIa.

Azepines↗
PubMed1992

[A case of giant pigmented nevus with multiple meningiomas].

A 36-year-old female had a giant congenital pigmented nevus on her anterior trunk. She complained of muscle weakness of the right arm and leg in August 1988, and she was admitted to our hospital to take medical examinations in September 1988. Neurological examination revealed right hemiparesis and exaggerated deep tendon reflexes. Three small falx meningiomas were shown on CT scans and MR images, but they did not appear to be causes of her symptoms. CT-myelography and MR images revealed an intradural extramedullary tumor spreading from the foramen magnum to C2. Oncotomy and C1 laminectomy were performed. Histological finding was compatible with transitional meningioma. Neurological symptoms markedly improved after operation. This patient is considered as a case of neurocutaneous syndrome with central nervous system tumors. Considering that both giant pigmented nevus and meningioma originate from neural crest, they appear to be closely related each other. Such a combination of giant pigmented nevus and meningioma has not yet been reported.

Adult↗
PubMed1992

[A pharmacokinetic study of intra-arterial chemotherapy for prophylactic treatment of liver metastasis after hepatectomy for liver cancer].

As a fundamental study of efficacy of intra-arterial administration using ADM, ERB and MMC for prophylactic treatment of liver metastasis after hepatectomy for liver cancer, the pharmacokinetics of three drugs (ADM 10mg (n = 5), ERB 20mg (n = 3) and MMC 6 mg (n = 3)) were studied in patients who underwent hepatectomy after intra-arterial injection. The hepatic extraction calculated from the areas under the plasma concentration time curve of both administrations was 40% in ADM, 60% in ERB, and 0% in MMC. From these findings, it is suggested that intra-arterial administration could reduce by half the systemic toxic side effects of ADM or ERB, but the advantage of intraarterial infusion of MMC was not obvious.

Chemotherapy, Adjuvant↗
PubMed1991

Potencies and stereoselectivities of enantiomers of huperzine A for inhibition of rat cortical acetylcholinesterase.

The stereoselectivities and mechanisms of the inhibition of rat cortical acetylcholinesterase by the enantiomers of huperzine A were determined. (-)-Huperzine A was the more potent enantiomer with a Ki value of 8 nM. (+)-Huperzine A inhibited the enzyme 38-fold less potently with a Ki value of 300 nM. Racemic huperzine A was about two-fold less potent than the more active isomer, (-)-huperzine A. The mechanism of inhibition of acetylcholinesterase for all three drugs was of the mixed linear competitive type.

Alkaloids↗