Search PubMed⌕ Search

Biomedical subjects

Y Hamada

Publications and source records attributed to Y Hamada.

At least 307 records · Page 17Linked to original sources
PubMed1995

An aldose reductase inhibitor, TAT, reduces ADP-induced platelet hyperaggregation in streptozotocin-induced diabetic rats with neuropathy.

To investigate the relationship between metabolic and vascular factors, especially polyol pathway and platelet aggregation, in the pathogenesis of diabetic neuropathy, the effects of a novel potent aldose reductase inhibitor, TAT ((5-(3-thienyl) tetrazol-1-yl) acetic acid monohydrate) on adenosine diphosphate-induced platelet aggregation, polyol contents in platelets, motor nerve conduction velocity (MNCV), and sciatic nerve blood flow (SNBF) were examined in streptozotocin-induced diabetic rats. Diabetic rats demonstrated hyperaggregation in response to adenosine diphosphate, accompanied by sorbitol and fructose accumulation and myoinositol depletion in platelets. Treatment with TAT improved these abnormalities in diabetic rats. A delayed MNCV and a reduced SNBF in diabetic rats were normalized by the administration of TAT. These observations suggest that increased polyol pathway activity plays an important role in platelet aggregation in the development of diabetic neuropathy and that aldose reductase inhibitor is useful for the treatment of diabetic neuropathy from the viewpoint not only of metabolic factors but also of vascular factors.

Adenosine Diphosphate↗
PubMed1995

[Role of interstitium in the regulation of renal tubular solute transport].

The physiological significance of the renal interstitium is reviewed with special reference to solute transport. The renal tubules and vasculatures participate in essential parts of the nephron functions. The renal interstitium, interposing among these structures, regulates solute transport across the renal tubules. In the renal cortex, changes in the interstitial pressure modulate the proximal tubular fluid reabsorption via paracellular shunt pathways. In the renal medulla, the interstitium may play an important role in the lateral diffusion of solutes and water, contributing to the mechanisms of urine concentration, as well as, medullary potassium recycling and ammonia excretion.

Animals↗
PubMed1995

[A case of giant bronchogenic cyst complicated with postoperative esophageal perforation].

A 42-year-old man with giant bronchogenic cyst occupied from the middle and posterior mediastinum was treated surgically. The tumor was stoutly adhered to anterior aspect of the esophagus and membranous portion of the right bronchus. In dissecting the tumor, muscular coat of the esophagus was partly severed, which was repaired interruptedly with absorbable suture material. However, esophageal perforation was detected by barium swallow on the 3rd postoperative day. Conservative therapy included intrathoracic drainage and antibiotics was successfully undertaken. It is imperative to dissect the tumor very carefully if the giant bronchogenic cyst adheres to the esophagus or other surrounding organs.

Adult↗
PubMed1995

[Solitary plasmacytoma of the rib--a case report and review of Japanese literatures].

A 72-year-old woman with solitary plasmacytoma of the right fifth rib was surgically treated. She underwent radical resection of the bony chest wall including the right fifth rib, the ribs above and below the involved rib, the intercostal muscle, and the parietal pleura. Histological finding of the tumor was plasmacytoma of the rib. The type of monoclonal protein was IgG and lamda. She is doing well one year and eleven months after surgery without any signs of recurrence. Solitary plasmacytoma is rare as compared with multiple myeloma. Patients with solitary plasmacytoma originating in the rib have a feasibility of operative indication, and radical treatment is expected to be by adequate surgical resection. Seventeen cases of solitary chest wall plasmacytoma described in the Japanese literature are reviewed.

Adult↗
PubMed1995

Hormone-induced bile flow and hepatobiliary calcium fluxes are attenuated in the perfused liver of rats made cholestatic with ethynylestradiol in vivo and with phalloidin in vitro.

The actions of vasopressin and glucagon, administered alone or together, were assessed on bile flow in perfused livers from rats made cholestatic by the injection of ethynylestradiol and from those allowed to recover from such treatment. Concomitant measurements were made of biliary calcium output as well as changes in the perfusate Ca2+ concentration, glucose output, and oxygen uptake. Experiments were also conducted where cholestasis was induced in vitro in the perfused liver by the infusion of phalloidin. In each case cholestasis was demonstrated to have occurred by a reduction in bile flow by approximately 50%. The data show that the transient increase in bile flow and bile calcium seen in control rat liver soon after the administration of vasopressin, particularly when coadministered with glucagon, is largely absent in cholestasis induced by ethynylestradiol and attenuated in cholestasis induced by phalloidin. At the same time the pattern of perfusate Ca2+ fluxes in ethynylestradiol-induced cholestasis shifts to one reflecting net efflux of the ion from the liver. The responses to glucagon administration alone contrast with those of vasopressin in that in the perfused liver of ethynylestradiol-treated rats, glucagon induces a pronounced and sustained increase in bile flow. In cholestasis induced by both ethynylestradiol and phalloidin, glucagon fails to induce an initial transient decrease in bile flow. The effects of glucagon, including enhancement of vasopressin-stimulated bile flow in control and in ethynylestradiol-treated rats, can be mimicked by dibutyryl cyclic adenosine monophosphate (cAMP). Changes in glucose output and oxygen uptake induced by both hormones are only slightly attenuated. The data show that the modulation of bile flow that occurs rapidly after the administration of vasopressin and glucagon to control perfused rat liver is altered in conditions of cholestasis induced by either ethynylestradiol or phalloidin.

Animals↗
PubMed1994

Activation of K+ channels by ritodrine hydrochloride in uterine smooth muscle cells from pregnant women.

This study investigated the mechanism of activation of K+ channels by ritodrine hydrochloride in human myometrial smooth muscle cells. The patch-clamp technique was used for recording single channel currents. Ritodrine (10(-5) M) activated two types of K+ channels in cultured uterine smooth muscle cells from pregnant women: the Ca(2+)-activated K+ (KCa) channel and the ATP-sensitive K+ (KATP) channel. Forskolin (10(-4) M), an activator of adenylate cyclase, and protein kinase A activated the KCa channel. In addition, 10(-4) M GTP activated the KCa channel in inside-out patches using a pipette containing 10(-5) M ritodrine. The KATP channel was activated by protein kinase A, but not by 10(-4) M GTP. The beta-adrenoceptor agonist ritodrine activates two types of K+ channels: the KCa channel via direct gating by GTP-binding proteins and possibly via cAMP-dependent phosphorylation, and the KATP channel possibly via cAMP-dependent phosphorylation. These mechanisms partially explain the relaxing effect of ritodrine hydrochloride.

Cells, Cultured↗
PubMed1994

Structure of ascidiacyclamide as the ethanol water solvate, a cytotoxic cyclic peptide from Ascidian.

The X-ray crystal structure determination of the C2H5OH.H2O solvate of ascidiacyclamide (C36H52N8O6S2), a cytotoxic cyclic peptide from marine tunicate Ascidian, revealed a C2-symmetric saddle-shaped rectangular conformation of the molecule. The water and ethanol molecules are located on the crystallographic diad axis and are held by hydrogen bonds and van der Waals contacts with the polar ring N atoms and nonpolar D-Val side-chain atoms, respectively. The molecular conformation and the interaction with solvent molecules are nearly the same as those of the compound with C2H5OH.2H2O [Ishida, In, Doi, Inoue, Hamada & Shioiri (1992). Biopolymers, 32, 131-143].

Animals↗
PubMed1994

Evaluation of the functional connectivity in the nervous system using time dependent scatter diagrams.

We investigated spike trains of the feline nervous system, which are considered to be non-stationary point processes characterized by changes of the functional interneuronal connectivities. Ordinary long-term averaged correlation methods are useful as processing time series data as a quasi-stationary point process, but not as a non-stationary point process. We depicted the joint impulse configuration scatter diagram proposed by D. H. Perkel et al. for subsets of the neural spike-train to find changes of functional connectivities. The time-dependent scatter diagram was generated by arranging these scatter diagrams in chronological order. Time-dependent scatter diagrams were generated for spike trains derived from the anterior ectosylvius sulcus, the coronal sulcus, the lateral bank of the presylvius sulcus, the medial wall of the presylvius sulcus, and the medial wall of the cruciate sulcus. The patterns of time-dependent scatter diagrams for these cortices are considered to change in relation to eye movement. Changes of these patterns correspond to those of the functional connectivities related to the dynamics of eye movement in the neural system.

Animals↗
PubMed1994

Patellamide A, a cytotoxic cyclic peptide from the ascidian Lissoclinum patella.

The structure of crystals of patellamide A (13-methyl-9,23-bis(1-methylethyl)-2,16-bis(1-methylpropyl)-14,-28-di oxa-7,21- dithia-3,10,17,24,29,30,31,32- octaaza-pentacyclo[24.2.1.1(5,8).1(12,15).1(19,22]dotriac onta-1(29),5,- 8(30),15(31),19,22(32)-hexaene-4,11,18,25-tetraone methanol solvate monohydrate, C35H49N8O6S2.-CH4O.H2O), a cytotoxic cyclic peptide having a non-C2-symmetric methyl group, shows the C2-symmetric and saddle-shaped rectangular conformation where the methyl group is disordered into two C2-symmetric positions. The water and methanol solvents were located on the crystallographic diad axis and were held by hydrogen bonds and van der Waals contacts with the polar ring N atoms and non-polar D-Val side-chain atoms, respectively.

Animals↗
PubMed1994

A ruptured thymic branch aneurysm mimicking a ruptured aortic aneurysm, with associated bronchial artery aneurysms: report of a case.

A 57-year-old woman who went into shock following an acute left hemothorax was operated on after stabilization under the diagnosis of a ruptured aortic aneurysm. A left fifth intercostal thoracotomy was done which revealed approximately 500 ml of bloody effusion in the extrapleural space and 2,000 g of clotted blood in the pleural cavity. While the aneurysm was initially thought to have originated in the isthmic or descending aorta, intraoperative findings revealed a swollen hematomatous thymus adherent to the aorta. A ruptured thymic branch aneurysm, 3 cm in diameter, was subsequently found in the resected hematomatous thymus. Histological examination also revealed several small aneurysms in the tortured bronchial arteries. Postoperative angiography showed a saccular aneurysm, 1.5 cm in diameter, and several smaller aneurysms in the bronchial artery of the left lung. The aneurysm was successfully treated by a transcatheter arterial embolization, and the patient has had no further symptoms since then. To our knowledge, there has been no other case of a ruptured thymic artery aneurysm reported in the literature, and only a few cases of bronchial artery aneurysms have been documented.

Aneurysm↗
PubMed1994

Hepatic encephalopathy due to congenital splenorenal shunts: report of a case.

A 76-year-old Japanese woman with hepatic encephalopathy was successfully treated for congenital splenorenal shunts by surgical intervention. The flow volume of the splenorenal shunts was 800 ml/min with a shunt pressure of 9.8 mmHg. The portal pressures before and after the shunt resection were 9 mmHg and 12 mmHg, respectively. The portal flows before and after the shunt resection were 230 ml/min and 470 ml/min, respectively. Therefore, both the hepatic sinusoid and the portal vein might provide good compliance for an increased portal flow volume load after shunt resection.

Aged↗
PubMed1994

Interaction of marine toxin dolastatin 10 with porcine brain tubulin: competitive inhibition of rhizoxin and phomopsin A binding.

Dolastatin 10, a cytostatic peptide containing several unique amino acid subunits, was isolated from the marine shell-less mollusk Dolabella auricularia. It inhibits microtubule assembly at concentrations below 5.0 microM (IC50, 3.0 microM) and causes formation of tubulin aggregates at higher (> 10 microM) concentrations in a somewhat different manner from that caused by vinblastine. Electron microscopical analysis showed irregular aggregates of microtubule proteins in the presence of 10 microM dolastatin 10. Dolastatin 10 inhibited the binding of both radiolabeled rhizoxin and phomopsin A to tubulin with inhibition constants (Ki) of 7 x 10(-8) M and 1 x 10(-7) M, respectively. The results suggest that at least one of the binding sites of dolastatin 10 on tubulin is the rhizoxin binding site.

Animals↗
PubMed1994

Phenytoin reduces neonatal hypoxic-ischemic brain damage in rats.

We investigated the possible protective effect of phenytoin on hypoxic-ischemic brain damage in neonatal rats. Six-day-old rats underwent ligation of the left carotid artery followed by exposure to an 8% oxygen atmosphere for 2.5 hrs. We sacrificed the animals 72 hrs later and assessed the hypoxic-ischemic brain damage histologically. Phenytoin (50 mg/kg), administered intraperitoneally 1 hr before the hypoxia, reduced hypoxic-ischemic infarction in the cerebral cortex and striatum, and attenuated neuronal necrosis in the hippocampus. The plasma concentration of phenytoin after injection was 11.1 +/- 1.9 micrograms/ml (mean +/- S.E.M.) at 1 hr and 22.9 +/- 1.4 micrograms/ml at 4 hrs. Percent volumes of the infarction calculated by dividing the sum of damaged areas by the total area in serial coronal sections were 79 +/- 3% (mean +/- S.E.M.) in vehicle controls versus 13 +/- 6% in phenytoin-treated pups in the cerebral cortex, and 79 +/- 4% in vehicle controls versus 12 +/- 5% in phenytoin-treated pups in the striatum. We semiquantitatively investigated the hypoxic-ischemic change in 5 hippocampal areas: dentate gyrus, CA4, CA3, CA1, and subiculum, in the dorsal hippocampus. Pre-hypoxic treatment with phenytoin reduced hypoxic-ischemic damage in all areas examined. When phenytoin was administered immediately after the hypoxia, there was no difference between vehicle-injected controls and phenytoin-treated pups. These results demonstrate that phenytoin can reduce neonatal hypoxic-ischemic brain damage.

Animals↗
PubMed1994

Crosstalk between calcium- and cyclic AMP-mediated signalling systems and the short-term modulation of bile flow in normal and cholestatic rat liver.

The flow of bile is subject to short-term modulation by glucagon and calcium-mobilizing hormones. Of potential relevance is the crosstalk between the second messenger-mediated signal transducing systems of these agonists. This latter point has revealed an area of investigation that should enable further insights to be made into a physiological network that interrelates bile flow, hepatocellular calcium movements and hormone action. This information in turn may provide insights into the etiology and treatment of human and animal diseases in which cholestasis is an underlying feature.

Animals↗
PubMed1994

Inhibitor of nitric oxide synthesis reduces hypoxic-ischemic brain damage in the neonatal rat.

We evaluated the neuroprotective effect of the nitric oxide synthesis inhibitor, NG-nitro-L-arginine in a neonatal hypoxic-ischemic rat model. Unilateral hypoxic-ischemic injury was produced in the brain of 7-d-old rats using a combination of a common carotid artery ligation and a hypoxic (8% oxygen) exposure for 2.5 h. In our experimental condition, rectal temperatures did not differ between NG-nitro-L-arginine-treated and saline-injected pups. We killed the animals 72 h later and assessed the hypoxic-ischemic brain damage histologically. NG-nitro-L-arginine (2 mg/kg) administered intraperitoneally 1.5 h before hypoxia resulted in 77% reduction of the infarcted hemispheric volume and 87% reduction of the infarcted striatal volume compared to saline injected controls. NG-nitro-L-arginine given 1.5 h before the insult also significantly prevented hypoxic-ischemic damage in the five hippocampal structures examined, dentate gyrus, CA4, CA3, CA1, and subiculum. NG-nitro-L-arginine administered immediately after hypoxia did not prevent hypoxic-ischemic brain damage. These results indicate that nitric oxide plays a key role in producing neonatal hypoxic-ischemic brain damage.

Animals↗
PubMed1994

Isolation of an ascitic oncodevelopmental protein exhibiting high sequence homology with calcium-binding protein MRP8.

A human oncodevelopmental protein (ODP) with a molecular size of 28 kDa was isolated, employing malignant ascitic fluid of an advanced mixed mesodermal tumor of the uterus, by anti-ODP coupled Affi-Gel 10 column chromatography, followed by preparative PAGE. The final preparation obtained with this procedure gave a single band exhibiting reactivity with an anti-ODP antibody on analytical sodium dodecyl sulfate-PAGE. The sequence of the first 20 N-terminal amino acids of this protein is identical with those of both the cystic fibrosis protein and Ca-binding protein MRP8 except at position 17, for which no result was obtained. Sequence analysis suggested that the protein shows 90% sequence homology with both these proteins.

Amino Acid Sequence↗