Biomedical subjects

J Yamamoto

Publications and source records attributed to J Yamamoto.

At least 145 records · Page 8Linked to original sources

PubMed1997

Intracerebroventricular injection of isoproterenol produces its analgesic effect through interleukin-1beta production.

The effects of isoproterenol, a beta-adrenoceptor agonist, on the production of interleukin-1beta in the brain and on mechanical nociception were examined in rats. Intracerebroventricular (i.c.v.) injection of isoproterenol at the dose of 3 microg/rat markedly induced interleukin-1beta mRNA in the molecular layer of the hippocampus, medial preoptic area, paraventricular thalamic nucleus, paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, dorsomedial hypothalamic nucleus and central gray 1 h after injection. In these regions, interleukin-1beta mRNA was expressed mainly in the glial cells. The thresholds to the mechanical stimulation to the hind paw were elevated by i.c.v. administration of isoproterenol (1 to 10 microg/rat). When isoproterenol was given at the dose of 3 microg/rat, the analgesic effect showed two peaks. The first peak was observed at 60 min after injection and the second was observed at 180 min. The second phase of analgesia was antagonized by coadministration of interleukin-1 receptor antagonist. These results suggest that isoproterenol produces an analgesic effect, at least in part, through the induction of interleukin-1beta expression in the brain.

Analgesics↗

PubMed1997

Screening and identification of yeast sequences that cause growth inhibition when overexpressed.

To isolate genes that negatively regulate cell growth, we constructed a galactose-inducible expression library with partially digested Saccharomyces cerevisiae genomic DNA fragments inserted downstream of the GAL10 promoter. In all, 240,000 yeast transformants were screened for lethality on galactose medium. From 17 such transformants identified, 16 nonoverlapping DNA sequences were obtained. Restriction mapping and determination of DNA sequences adjacent to the GAL10 promoter indicated that the inserts encoded part or all of the URA2, RBP1, TPK3, SAC7, BOI1, and BNI1 genes, and also open reading frames (ORFs) from chromosomes IV, V, IX, XI, and XIII. Some of the identified sequences lacked the amino-terminal sequences of the ORFs, suggesting that truncated forms of the proteins might be necessary for growth inhibition. The sequence of the pGA108 insert was highly homologous to the telomeric X-element and contained an ARS consensus sequence, suggesting a possible growth inhibitory effect of an RNA molecule. Overexpression of the BNI1 deltaN and BOI1 deltaN genes, which lacked amino-terminal sequences, was associated with phenotypes similar to those of mutants defective in bud formation. Overexpression of the GIN4 and GIN12 sequences induced elongated buds and a G2/M arrest-like phenotype, respectively. The phenotypes induced by the overexpression of our cloned sequences could result from either a dominant-positive or a dominant-negative effect and, unexpectedly, in one case from an effect of an RNA.

Amino Acid Sequence↗

PubMed1997

Adjuvant effect of argatroban on staphylokinase induced thrombolysis of platelet rich thrombi in rat mesenteric venules in vivo.

Effective, therapeutic thrombolysis should not only promote dissolution of fibrin but should also regulate continued thrombin-induced fibrin formation and the accumulation of platelets on the thrombotic lesion. The aim of the present study was to assess the use of a synthetic, low molecular weight thrombin inhibitor, argatroban in association with a well defined thrombolytic agent in a reproducible animal model of thrombolysis in vivo. Thrombi were formed in rat mesenteric venules with a helium neon (He-Ne) laser in the presence of Evans blue and were stabilised for 10 minutes. Thrombi formed in this manner were shown by transmission electron microscopy to be composed mainly of platelets. Thrombolysis was induced with recombinant staphylokinase in the presence and absence of argatroban and the process was monitored using computerised image analysis. Co-infusion of argatroban at a dose of 2.0 mg/kg/h with staphylokinase significantly enhanced the rate of thrombolysis. The results suggested that administration of the thrombin inhibitor together with the fibrinolytic agent moderated platelet-dependent mechanisms and led to a more rapid restoration of blood vessel patency.

Animals↗

PubMed1997

Detection of a prothrombotic state after acute aerobic exercise.

Angina, myocardial infarction, and sudden cardiac death are associated with thrombus formation in coronary arteries. It is generally believed that these conditions benefit from long-term exercise. However, the evidence for such amelioration or prevention is inconclusive and so is the mechanism through which long-term exercise exerts its beneficial effect on various ischaemic conditions. Because of the thrombotic events, the effects of exercise on platelet reactivity, blood coagulation and fibrinolysis have been extensively studied, but the findings are not consistent (1-9). This is mainly due to methodological problems. Analysis of platelet response to a variety of agonists and the dozen of coagulation and fibrinolysis variables makes the assessment of the overall platelet function, coagulation and fibrinolysis status extremely difficult.

Adult↗

PubMed1997

The antithrombotic effect of synthetic low molecular weight human factor Xa inhibitor, DX-9065a, on He-Ne laser-induced thrombosis in rat mesenteric microvessels.

The effect of a synthetic low molecular weight factor Xa (FXa) inhibitor, DX9065a, on thrombosis in vivo were examined in a rat animal model using a Helium-Neon (He-Ne) laser method. DX-9065a administered either intravenously or orally promoted anti factor Xa activity in a dose dependent manner. Anti Xa activity was maximal immediately after intravenous injection and persisted for approximately 30 minutes. Inhibitory activity was maximal 15-30 minutes after oral administration and persisted for approximately 90 minutes. Similarly DX-9065a inhibited platelet-rich thrombosis formation in mesenteric arterioles and venules. In these instances inhibition was relatively transient after intravenous injection (10-20 minutes), but persisted for more than 3 hours after oral administration. The minimum effective doses of DX-9065a given intravenously and orally were 3.89 mg/kg and 25.9 mg/kg, respectively. The results confirmed that DX-9065a selectively modulates thrombotic mechanisms, and suggest that development of this synthetic FXa antagonist could constitute an effective intravenous and oral antithrombotic agent.

Animals↗

PubMed1997

Simple technique for pancreatogastrostomy and the histological findings of pancreatogastric anastomosis.

The leakage of pancreatic juice is the most serious complication after pancreatoduodenectomy. In an attempt to lessen the incidence of this complication, we have developed a simple technique for the anastomosis of pancreatogastrostomy. Since March 14, 1995, we have already performed surgical procedures on 8 cases of pancreatogastrostomy using this technique and as yet have never experienced fatal complications. We report the autopsy findings of pancreatogastric anastomosis histologically. The specimen taken from the anastomosis reveals good mucosal continuity. This result suggests the importance of reliable sutures between the pancreatic parenchyma and the full thickness of the gastric wall for the anastomosis of pancreatogastrostomy.

Adenocarcinoma↗

PubMed1997

Clinical significance of the DNA index in hematogenous dissemination of aneuploid colorectal cancer.

The DNA index (DI), defined as the ratio of the G0/G1 channel number of tumor cells to the G0/G1 channel number of stromal cells, was analyzed in 121 aneuploid colorectal cancers. In patients with aneuploid tumors, a high DI significantly correlated with tumor penetration beyond the proper muscle layer, positive vascular invasion, and the presence of liver metastasis. This observation led us to conclude that a high DI is likely to be associated with hematogenous dissemination in aneuploid colorectal cancer.

Aneuploidy↗

PubMed1997

Cortical and hippocampal EEG power spectra in animal models of schizophrenia produced with methamphetamine, cocaine, and phencyclidine.

Cortical and hippocampal EEGs in animal models of schizophrenia were compared to those obtained with psychotomimetics or antipsychotic agents by utilizing power spectral analysis. Models of positive schizophrenic symptoms were created with methamphetamine (MAP) and cocaine, and a model of both negative and positive symptoms was created with PCP. MAP caused a prolonged decrease in the cortical EEG power spectra, cocaine caused a marked decrease for a short time, and PCP produced no significant changes. In the hippocampal spectra, MAP induced a marked increase in the T2(6.0-7.9 Hz)/ T1(4.0-5.9 Hz) ratio, PCP caused a decrease of this ratio after an initial increase, and cocaine produced no significant change. (An increase in the T2/T1 ratio represents a shift of theta waves to higher frequencies.) Since apomorphine (a DA agonist) and MK-801 (an NMDA antagonist) caused the T2/T1 ratio to increase, positive schizophrenic symptoms caused by MAP may be related to the DA and NMDA systems. 3-PPP (a sigma agonist) caused biphasic changes similar to those induced by PCP. Haloperidol and chlorpromazine caused a decrease of the T2/T1 ratio. These results indicate that cortical and hippocampal EEG power spectra (especially the hippocampal T2/T1 ratio) can be used to characterize both qualitatively and quantitatively models of schizophrenia.

Adrenergic Agents↗

PubMed1997

Amelioration of methotrexate-induced malabsorption by vitamin A.

Methotrexate (MTX) induces damage to the small intestine, resulting in malabsorption and diarrhea. We found that the coadministration of vitamin A (VA) with MTX protected the small intestine from MTX-induced damage. In this study, the permeability of D-glucose, D-xylose and L-leucine through the small intestine of rats treated with MTX and/or VA was studied using everted segments of small intestine. MTX treatment decreased permeability and VA coadministration prevented the decrease. The transport of D-glucose in the small intestine of MTX plus VA- and VA-treated rats and of control rats followed Michaelis-Menten kinetics, in contrast to the transport kinetics in MTX-treated rats. The pharmacokinetics of orally administered [14C]-D-glucose in control rats and MTX- and/or VA-treated rats was also studied. The bioavailability of D-glucose in MTX-treated rats was lower than in the other three groups. VA coadministration improved the bioavailability of D-glucose. Thus, it seems likely that VA ameliorates MTX-induced malabsorption.

Administration, Oral↗

PubMed1997

Expression of von Willebrand factor, P-selectin (CD62P) and thrombomodulin in human endothelial cells in culture modulated by cyclosporin A.

Endothelial cells were isolated from human umbilical veins and from saphenous veins and were cultured in the presence and absence of cyclosporin A (CSA). Cell morphology and growth characteristics were monitored continuously by video recording microscopy. The cells and culture supernatants were analysed for von Willebrand Factor (VWF), P-Selectin (CD62P) and thrombomodulin (TM) by immunocytochemistry and immunoassay. CSA had little effect on confluent cells in culture. In contrast, the characteristics of both umbilical vein and saphenous vein cells were markedly altered when CSA was added to subconfluent cultures. Under these conditions, CSA did not appear to be directly cytotoxic at the concentrations used but marked changes in cell morphology including the appearance of large multinucleate forms were recorded. Increased amounts of VWF and TM were detected in the culture supernatants of cells grown continuously in the presence of CSA and correspondingly depressed expression of cell associated antigens was observed. Heterogeneous and depressed distribution of CD62P was seen after 5-6 days culture but cellular expression of this ligand did not appear to be affected specifically by the presence of CSA. In addition, mechanically disrupted confluent endothelial cells failed to recover in the presence of CSA as effectively as similar cells grown in the absence of CSA. The results showed that CSA disturbed actively growing cells more severely than quiescent cells and might help to clarify the role of CSA in vascular disturbances in vivo.

Cells, Cultured↗

PubMed1997

Intrahepatic cholangiocarcinoma presenting intrabile duct extension: clinicopathologic study of five resected cases.

Intrahepatic cholangiocarcinoma, which is ordinarily a very invasive tumor and often takes a rapid and fatal course, sometimes shows macroscopic intrabile duct extension. The purpose of this study is to illustrate the clinicopathologic features of this variant of intrahepatic cholangiocarcinoma, which has occasionally been reported. Five cases of the tumor with gross extension to the bile duct lumen were studied to determine their clinical and pathologic features. The tumor showed intrabile duct growth and superficial mucosal spread in two patients. In two other patients, an apparent mass lesion accompanied the intraluminal component. In the remaining patient, a polypoid tumor infiltrated the portal tract of the left lateral segment, where it had arisen. Microscopic examination did not reveal any vascular involvement or intrahepatic or lymph node metastasis. All of the patients are alive without recurrence, except for Patient 1 who died 7 years and 7 months after surgery from a rapidly growing tumor in the liver remnant. Intrabile duct growth of intrahepatic cholangiocarcinoma may reflect indolent biological behavior and thus warrants an aggressive surgical approach, which appears to give a good prognosis.

Adenocarcinoma↗

PubMed1997

Retroperitoneal schwannoma mimicking hepatic tumor in the caudate lobe.

We report a 41-year-old woman with a retroperitoneal schwannoma mimicking hepatic tumor in the caudate lobe. Dynamic computed tomography in the early phase showed an enhanced tumor (2.7 cm in diameter) in the Spiegel lobe of the liver, which compressed the inferior vena cava (IVC). We also performed left hepatic angiographic computed tomography, and found that the tumor was less enhanced. The patient underwent laparotomy under a preoperative diagnosis of primary hepatic caudate tumor with faint neovascularity. At surgery, the tumor was found to be located between the left caudate lobe and the IVC, and was resected as being of a retroperitoneal origin. This case illustrates that tumor location must be determined with great care when the mass seems to exist at the dorsal edge of the liver, and especially when the tumor is hypovascular.

Adult↗

PubMed1997

Malignant melanoma of the uterine cervix: a case report.

We present case of a 57-year-old Japanese woman a 9 cm-size primary malignant melanoma of the uterine cervix. MRI demonstrated a low-signal T1-weighted spin echo image and hyperperfusion indicated by Gd-DTPA enhancement. The sequence analysis of the MTS1/CDK4I gene revealed no deletion or mutation. The results of cytological, pathological, and electron microscopy tests are also presented.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1997

Analysis of biliary drainage in the caudate lobe of the liver: comparison of three-dimensional CT cholangiography and rotating cine cholangiography.

PURPOSE: To evaluate the bile duct anatomy of the caudate lobe without disease involvement with use of three-dimensional (3D) cholangiography and to compare the usefulness of this technique with that of rotating cine cholangiography. MATERIALS AND METHODS: In 12 patients with obstructive jaundice but without lesions at the hepatic hilum who underwent percutaneous transhepatic biliary drainage, serial examination was performed with cine cholangiography and helical computed tomography (CT). From helical CT scans, 3D cholangiograms were reconstructed. Cine and 3D cholangiograms were evaluated and compared simultaneously. RESULTS: In the 12 patients, 40 branches of the caudate lobe were detected with 3D cholangiography (mean, 3.3 branches per patient), while 31 were detected with cine cholangiography (mean, 2.6 branches per patient). The difference in detection rate was significant (P < .01). Nine (23%) of 40 branches were detected with 3D cholangiography alone, and all 31 branches detected with cine cholangiography were also detected with 3D cholangiography. CONCLUSION: 3D cholangiography was superior to cine cholangiography in assessment of bile duct anatomy of the caudate lobe of the liver because 3D cholangiography eliminated the overlap of different branches of the bile duct.

Aged↗

PubMed1997

Hepatic tumor invasion of bile ducts: wedge-shaped sign on MR images.

PURPOSE: To clarify the diagnostic importance of wedge-shaped areas of increased signal intensity that surround liver tumors on T1-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: In five patients with hepatic tumors, T1-weighted MR images that demonstrated wedge-shaped areas of increased signal intensity in the liver were reviewed; findings were compared with those at surgical and histologic examinations. RESULTS: MR images showed localized intrahepatic bile duct dilatation lateral (three patients) and medial (two patients) to liver tumors within the wedge-shaped areas. At histopathologic examination, intraductal tumor growth was seen in local bile ducts in the same areas in five patients, and lipofuscin deposits were seen in the cytoplasm of atrophic hepatocytes in three patients. CONCLUSION: On T1-weighted images, wedge-shaped areas of increased signal intensity associated with liver tumors indicate intraductal tumor extension in intrahepatic bile ducts. T1 shortening is possibly caused by lipofuscin deposits in atrophic hepatocytes.

Adult↗

PubMed1997

GTS-21, a nicotinic agonist, protects against neocortical neuronal cell loss induced by the nucleus basalis magnocellularis lesion in rats.

Effect of subchronically administered GTS-21 [3-(2,4-dimethoxybenzylidene)-anabaseine dihydrochloride], a selective nicotinic agonist, on neuronal cell loss caused by nucleus basalis magnocellularis (nBM) lesion was studied in rats. After 2 weeks of bilateral nBM excitotoxic lesion, GTS-21 was orally administered once daily for 20 weeks. Neuronal cell loss was observed in layers II-III of the parietal cortex in the lesioned control rats. GTS-21 significantly attenuated the neuron loss in these layers. These results suggest that GTS-21 exhibits a protective action against the neuronal cell death in the parietal cortex and may have a beneficial effect on neurodegenerative disorders such as an Alzheimer-type disease.

Animals↗

PubMed1997

The differential involvement of von Willebrand factor, fibrinogen and fibronectin in acute experimental thrombosis in rat cerebral and mesenteric microvessels.

Arterial thrombi are primarily composed of platelets. Platelets are bound to injured endothelial cells, sub-endothelial matrices, and other platelets by a range of adhesive proteins. Some of these reactions are governed by shear forces. The role of adhesive proteins in the pathogenesis of arterial thrombosis is not fully understood. The aim of this study was to examine the involvement of von Willebrand factor (vWF), fibrinogen (Fg), and fibronectin (FN) in the formation of microvascular thrombi in vivo using a helium-neon laser-induced thrombosis method. Transmission electron microscopy demonstrated that laser irradiation resulted in platelet-rich thrombosis in arterioles and venules, and revealed that this occurred in the absence of endothelial denudation. The mean wall shear rates in mesenteric arterioles and venules were 641 +/- 40 and 280 +/- 20 s-1, respectively. Shear rates increased approximately fivefold in arterioles and tenfold in venules during the formation of occlusive thrombi. Antibody to vWF inhibited thrombosis in arterioles and venules. Antibodies to Fg and FN inhibited thrombosis in venules but not in arterioles. These results confirm that vWF, Fg and FN were involved in thrombogenesis in vivo and demonstrated that significantly higher shear rates were required for the reactions involving vWF than those involving either Fg or FN.

Adhesiveness↗

PubMed1997

Effect of arachidonate on lipid metabolism in ethanol-treated rats fed with lard.

Two groups of rats, ethanol-treated and sucrose-administered control rats, were fed diets with different AA content (0, 2 and 3% weight) for 14 days. Ethanol was administered by gavage at a single daily dose of 3 g/kg body weight. The ethanol-treated rats showed significantly higher levels (p < 0.01) of serum ALT activity. The dietary AA supplement lowered the serum ALT activity and liver triglyceride both in control and ethanol-treated rats. Significantly lower levels of 20:4n - 6 and 20:4n - 6/18:2n - 6 ratio and higher levels of 18:1n - 9 in both the serum and liver triglyceride were observed in the ethanol-treated rats. The AA-supplemented diet induced a marked increase of 20:4n - 6 and subsequent significant decrease of 18:2n - 6 both in the liver and serum phospholipid in control and ethanol-treated rats. 18:1n - 9 in the serum and liver triglyceride in both groups was also markedly decreased by AA supplement. No significant difference was observed in the liver 6-keto-PGF(1 alpha) level between the ethanol-treated and control rats. In the ethanol-treated rats, the level of 6-keto-PGF(1 alpha) was elevated in the rats fed the 3% AA-supplemented diet. Though the liver leukotriene B4 levels were increased by ethanol administration in all rats, these levels were not increased by dietary AA.

6-Ketoprostaglandin F1 alpha↗