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Biomedical subjects

T Yamaguchi

Publications and source records attributed to T Yamaguchi.

At least 397 records · Page 22Linked to original sources
PubMed2000

[Endonasal transsphenoidal surgery under local anesthesia for elderly patient with pituitary tumor: case report].

We present a surgical case under local anesthesia of an 88-year-old woman suffering from visual disturbance caused by pituitary adenoma. Magnetic resonance (MR) imaging showed a large pituitary tumor with suprasellar extension compressing the chiasmatic nerve. Neither she nor her family would agree to surgical therapy. However, when we proposed surgery under local anesthesia, they accepted it. Partial removal of the tumor via the endonasal transsphenoidal approach was carried out, uneventfully. The nasal surface was infiltrated with 4%-Xylocaine prior to the ordinary xylocaine injection to the nasal mucosa. The patient did not complain of any pain associated with the surgical procedure, including saline injection to the subarachnoid space through spinal drainage. The postoperative course was fine except for the temporarily appearance of diabetes insipidus. Postoperative MR imaging showed complete relief of compression to the chiasmatic nerve. Her visual field was improved dramatically. Endonasal transsphenoidal surgery under local anesthesia is thought to be one of the most useful methods of choice, especially in cases of elderly patient with pituitary tumor.

Adenoma↗
PubMed2000

[Does quinapril improve coronary vasoconstriction in vasospastic angina?].

OBJECTIVES: Endothelial dysfunction is one of the important mechanisms of coronary spasm. Recently, the angiotensin converting enzyme (ACE) inhibitor quinapril, which has a high affinity for vascular ACE, has improved endothelial dysfunction in coronary artery disease. This study investigated whether quinapril improves coronary vasoconstriction induced by acetylcholine in vasospastic angina. METHODS: Twenty-four patients with vasospastic angina without significant organic stenosis diagnosed by the acetylcholine provocation test (vessel with spasm defined as > or = 90% stenosis provoked with chest pain and/or ischemic ST change) were enrolled in this study. Patients were randomly assigned to 2 groups: the quinapril group (receiving quinapril 20 mg/day, n = 12), and the non-quinapril group (not receiving quinapril, n = 12). All patients received calcium antagonist. Six months later, coronary angiography was repeated and changes in coronary spasm were compared between the groups. Seven patients were withdrawn from this study, so 17 patients were evaluated (the quinapril group: 8 patients, the non-quinapril group: 9). RESULTS: Angina symptoms were completely or almost suppressed in all patients during the study period. Angiographically, the number of patients with improvement of spasm, patients with deterioration of spasm and patients with stability of spasm were 1, 0, 7 in the quinapril group versus 0, 1, 8 in the non-quinapril group, respectively. There was no significant change between the 2 groups. Quantitative angiographic analysis showed that the coronary spasm rate (percentage of minimal lumen diameter at the site of spasm after administration of acetylcholine to minimal lumen diameter after administration of isosorbide dinitrate) at the first and second angiography were 71 +/- 10% and 62 +/- 21% in the quinapril group versus 73 +/- 14% and 67 +/- 15% in the non-quinapril group, respectively. There were no significant interval changes between the 2 groups (p = 0.60). CONCLUSIONS: Our results did not indicate that quinapril had improved coronary vasoconstriction induced by acetylcholine in patients with vasospastic angina.

Acetylcholine↗
PubMed2000

[Analysis of ischemic stroke in patients aged up to 50 years].

BACKGROUND AND PURPOSE: Ischemic stroke in young adults has not fully been studied in Japan. The purpose of this study is to clarify the clinical features and pathogenetic mechanisms of ischemic stroke in young adults. METHODS: From January 1990 to June 2000, 133 (7.1%) of 1,862 consecutive patients with ischemic stroke were aged 16 to 50 years (92 men and 41 women, aged of 42.6 +/- 7.7 years). We divided the patients into three groups according to the age of stroke onset; 16 to 40 (group A, n = 38), 41 to 45 (group B, n = 33), and 46 to 50 years (group C, n = 62). Sex, vascular risk factors including hypertension, diabetes mellitus, hyperlipidemia and smoking, cerebrovascular lesions, potential cardiac sources of emboli (emboligenic cardiac diseases), and clinical categories of stroke were examined. We compared them among the three groups. RESULTS: Men predominated in the all groups. Patients in the group C had more frequently hypertension (p < .0005) and diabetes mellitus (p < .05) than those in the group A and B. The vertebrobasilar infarcts were often revealed in the group A but not in the group B and C (p < .01). No significant difference was observed about the incidence of emboligenic cardiac diseases among the three groups. Out of 46 emboligenic cardiac diseases, the most frequent one was patent foramen ovale (15 patients), whereas nonvalvular atrial fibrillation was documented only in five. Fourteen of 20 patients with significant atherosclerotic arterial lesions were found in the group C, whereas 13 of 16 patients with nonatherosclerotic vasculopathies in the group A. Ulcerated atheroma in the aortic arch was detected in two patients, both in the group C. Overall, clinical categories of stroke were identified as lacunar (Lac) in 34 patients (26%), atherothrombotic (AT) in 16 (12%), cardioembolic (CE) in 44 (33%), miscellaneous (Misc) in 27 (20%), and undetermined in 12 (9%). The most frequent cause of Misc (nine patients) was arterial dissection, occurring mostly in the vertebrobasilar system (eight of nine patients). Misc was most frequent in the group A (p < .0001), and Lac was so in the group C (p < .001). Seventy-six percent of patients in the group A and 61% of those in the group B were attributed to nonatherosclerotic causes. In contrast, 61% of patients in the group C had atherosclerotic causes. CONCLUSIONS: Incidence of athero- and arteriosclerosis as causes of ischemic stroke was apparently increased beyond 45 years of age. Patients < or = 45 years are likely to have various and unique etiologies for ischemic stroke. A specific diagnostic approach is strongly recommended for young patients with ischemic stroke.

Adolescent↗
PubMed2000

A study of orientation in a zero gravity environment by means of virtual reality simulation.

When the International Space Station (ISS) is completed and starts its operation, crew members will be stationed for three months or more in orbit aboard the ISS. As they stay longer in the space environment, "habitability" for them will become most important in the design of the interior space. One of the problems about habitability in a zero gravity (0 G) environment is disorientation. Crew members have difficulty in discriminating between "up" and "down" and more serious disorientations may cause space motion sickness. Crew members rely on visual perception to orient themselves because they can't use their sense of equilibrium in a 0 G environment. Although color and the direction of equipment of Space Shuttles or modules has been considered, no systematic study has been conducted on interior space. This study intended to clarify how people acquire visual information and recognize their orientation in a 0 G environment by an experiment in which a subject wears a head-mounted display (HMD) and enters a virtual weightless state represented by computer graphics (CG). Visual information of a room and the degree-of-freedom of motion were varied to examine the influence of the conditions on such a simple task as movement through several connected modules, and the performance and the behavior of each subject were investigated.

Humans↗
PubMed1999

Extracellular calcium-sensing receptor induces cellular proliferation and activation of a nonselective cation channel in U373 human astrocytoma cells.

A receptor for extracellular calcium ions (Ca2+o), cloned from parathyroid gland, serves a critical function in Ca2+o homeostasis by regulating PTH release via "sensing" of its physiological agonist, Ca2+o. Its cloning from rat striatum revealed that the extracellular calcium-sensing receptor (CaR) could be involved in sensing ambient Ca2+o within the brain, where Ca2+ plays key roles in virtually all aspects of central nervous system (CNS) function. The CaR is expressed in neurons, oligodendrocytes, microglia and the human astrocytoma cell line, U87 where its functions include control of cellular proliferation and modulation of ion channels, such as outward K+ channels and nonselective cation channels (NCC). In this report, we have shown that the CaR is expressed in U373 cells as assessed by RT-PCR using CaR-specific primers followed by sequencing of the amplified products, by Northern blot analysis using a CaR-specific probe as well as by Western analysis utilizing a specific polyclonal anti-CaR antiserum. Furthermore, agents known to activate the cloned CaR induce increases in cellular proliferation and the open probability of an NCC. Thus our study strongly suggests that elevated levels of Ca2+o, acting via the CaR, activate an NCC that could contribute to the associated CaR-induced stimulation of proliferation.

Animals↗
PubMed1999

Cross-reaction of chalcone synthase and stilbene synthase overexpressed in Escherichia coli.

Chalcone synthase (CHS) and stilbene synthase (STS) are related plant polyketide synthases belonging to the CHS superfamily. CHS and STS catalyze common condensation reactions of p-coumaroyl-CoA and three C(2)-units from malonyl-CoA but different cyclization reactions to produce naringenin chalcone and resveratrol, respectively. Using purified Pueraria lobata CHS and Arachis hypogaea STS overexpressed in Escherichia coli, bisnoryangonin (BNY, the derailed lactone after two condensations) and p-coumaroyltriacetic acid lactone (the derailed lactone after three condensations) were detected from the reaction products. More importantly, we found a cross-reaction between CHS and STS, i.e. resveratrol production by CHS (2.7-4.2% of naringenin) and naringenin production by STS (1.4-2.3% of resveratrol), possibly due to the conformational flexibility of their active sites.

Acyltransferases↗
PubMed1999

Induction of heme oxygenase-1 suppresses venular leukocyte adhesion elicited by oxidative stress: role of bilirubin generated by the enzyme.

This study aimed to examine whether an elevated activity of heme oxygenase (HO)-1 in the tissue attenuates endothelial cell-leukocyte interactions microvessels in vivo. When rats were pretreated with an intraperitoneal injection of hemin, an HO-1 inducer, mesenteric tissues, including their microvessels, displayed a marked induction of HO-1 concurrent with an increase in plasma concentrations of bilirubin-IXalpha, the product of HO-catalyzed degradation of protoheme IX. In these rats, oxidative stress such as superfusion with H(2)O(2) and ischemia-reperfusion of the tissues neither induced rolling nor exhibited adherent responses of leukocytes in venules. In contrast, the oxidative stresses evoked marked rolling and adhesion of leukocytes in the control rats without HO-1 induction. The HO-1 induction also downregulated leukocyte adhesion elicited by other pro-oxidant stimuli such as N(omega)-nitro-L-arginine methyl ester. The decreases in the oxidant-elicited leukocyte adhesive responses under HO-1-inducing conditions were restored by perfusion with zinc protoporphyrin-IX, an HO inhibitor, but not with copper protoporphyrin-IX, which did not inhibit the enzyme. Furthermore, the effects of zinc protoporphyrin-IX were repressed by superfusion with bilirubin or biliverdin at the micromolar level, but not by the same concentration of carbon monoxide, another product of HO. These results indicate that induction of the HO-1 activity serves as a potential stratagem to prevent oxidant-induced microvascular leukocyte adhesion through the action of bilirubin, a product of HO reaction.

Animals↗
PubMed1999

Commitment of neutrophilic differentiation and proliferation of HL-60 cells coincides with expression of transferrin receptor. Effect of granulocyte colony stimulating factor on differentiation and proliferation.

To examine the regulatory mechanisms of proliferation and maturation in neutrophilic lineage cells, we have tried to sort dimethyl sulfoxide (Me(2)SO)-treated HL-60 cells into transferrin receptor (Trf-R) positive (Trf-R(+)) and negative (Trf-R(-)) cells. Differentiated Trf-R(-) cells expressed more formyl-Met-Leu-Phe receptor (fMLP-receptor) and ability of O-(2) genaration, as markers of differentiation, than Trf-R(+) cells, and Trf-R(-) cell differentiation was markedly accelerated by the incubation with granulocyte colony stimulating factor (G-CSF). On the other hand, Trf-R(+) cells had a tendency to proliferate rather than differentiate, and proliferation was enhanced by G-CSF. These results indicate that Trf-R expression coincides with the commitment to proliferate or differentiate of HL-60 cells, and G-CSF accelerates these commitments. G-CSF-induced tyrosine phosphorylation of STAT 3 in Trf-R(-) cells much more than in Trf-R(+) cells. Protein 70 S6 kinase expression was higher in Trf-R(+) cells than in Trf-R(-) cells. Furthermore, p70 S6 kinase was hyperphosphorylated by G-CSF in Trf-R(+) cells, but not in Trf-R(-) cells. Rapamycin, an inhibitor of p70 S6 kinase activity, inhibited G-CSF-dependent proliferation of Trf-R(+) cells and increased fMLP-R expression on these cells. These results suggest that commitment to proliferation and differentiation in Me(2)SO-treated HL-60 cells is preprogrammed and correlated with Trf-R expression, and G-CSF potentiates the cellular commitment. STAT 3 may promote differentiation of Me(2)SO-treated HL-60 cells into neutrophils, while p70 S6 kinase may promote proliferation and negatively regulate neutrophilic differentiation.

Cell Differentiation↗
PubMed1999

Mode analysis of a fatty acid molecule binding to the N-terminal 8-kDa domain of DNA polymerase beta. A 1:1 complex and binding surface.

We reported previously that long-chain fatty acids are potent inhibitors of mammalian DNA polymerase beta. At present, based on information available from the NMR structure of the N-terminal 8-kDa domain, we examined the structural interaction with the 8-kDa domain using two species, C(18)-linoleic acid (LA) or C(24)-nervonic acid (NA). In the 8-kDa domain with LA or NA, the structure that forms the interaction interface included helix-1, helix-2, helix-4, the three turns (residues 1-13, 48-51, and 79-87) and residues adjacent to an Omega-type loop connecting helix-1 and helix-2 of the same face. No significant shifts were observed for any of the residues on the opposite side of the 8-kDa domain. The NA interaction interface on the amino acid residues of the 8-kDa domain fragment was mostly the same as that of LA, except that the shifted cross-peaks of Leu-11 and Thr-79 were significantly changed between LA and NA. The 8-kDa domain bound to LA or NA as a 1:1 complex with a dissociation constant (K(D)) of 1.02 or 2.64 mM, respectively.

Animals↗
PubMed1999

Inhibition of cancer cell growth by polyinosinic-polycytidylic acid/cationic liposome complex: a new biological activity.

A complex of polyinosinic-polycytidylic acid [poly(I) x poly(C)] and cationic liposome (LIC) inhibited the growth of many tumor cell lines at low concentration in vitro, but poly(I) x poly(C) alone had no such antiproliferative effect. The IC50 values of LIC against the tumor cells ranged from 0.1 to 1000 ng/ml. LIC had strong cytotoxic effects on malignant cells of epithelial and fibroblastic origin from various tissues and was also effective against Adriamycin-resistant tumor cells. LIC did not significantly affect the growth of lymphoma cells, leukemia cells, normal diploid fibroblasts, or primary liver cells at concentrations up to 10 microg/ml. The mechanism of the antiproliferative effect of LIC against malignant cells was the induction of apoptosis. LIC induced the fragmentation of nuclear DNA and the degradation of rRNA in tumor cells. The DNA fragmentation occurred within 1-5 h after the addition of LIC, and both the fragmentation and the inhibition of cancer-cell growth were suppressed by a nuclease inhibitor. In contrast, caspase inhibitors did not affect the antiproliferative activity of LIC. These results suggest that LIC induced apoptosis in malignant cells through the direct activation of nucleases and not through the activation of caspases. LIC reduced the incidence and the size of metastatic liver-cancer tumors in two different mouse metastatic liver-cancer models using human colon carcinoma cells. Histochemical analysis revealed that the KM12-HX cells in the tumor nodules were undergoing apoptosis; therefore, LIC also induced the apoptosis of tumor cells in vivo. In these animal models, LIC caused no observed changes in normal hepatocytes.

Animals↗
PubMed1999

Investigating centre effects in a multi-centre clinical trial of superficial bladder cancer.

This paper examines the amount of variation among centres and estimates the overall effect of therapy in a multi-centre cancer clinical trial with censored failure time data. To investigate the centre effects, the variation in the treatment effect must be taken into consideration in addition to the variation in the baseline risk. We treat centre effects as random ones and extend the penalized partial likelihood approach proposed by McGilchrist to estimate the treatment-by-centre interaction as well as the baseline risk. This method is applied to data from a superficial bladder cancer clinical trial investigating the efficacy of intravesical chemotherapy after transurethral resection. In this trial, although there exists some degree of centre variation, especially in the baseline risk, the treatment is effective in preventing recurrence among the participating centres. This result indicates that the treatment effect is generalizable to the target population.

Administration, Intravesical↗
PubMed1999

Differences in mucus and K-ras mutation in relation to phenotypes of tumors of the papilla of vater.

BACKGROUND: To investigate their hypothesis that K-ras mutation is correlated with epithelial metaplastic change, the authors classified tumors of the papilla of Vater histologically and according to mucin histochemistry as either intestinal type (complete or incomplete) or pancreaticobiliary type (ordinary or metaplastic) and analyzed the tumors for K-ras mutation during tumorigenesis. METHODS: Fifty-two tumors of the papilla of Vater (5 adenomas, 24 carcinomas with adenoma component, and 23 carcinomas) obtained from surgical specimens were evaluated. The mucus phenotype was analyzed with MUC1, MUC2, MUC5AC, sialyl Lewis(a) (CA 19-9), HID-AB, and ConA III stainings. K-ras codon 12 mutation was detected by nested polymerase chain reaction (PCR)-restriction fragment length polymorphism and enriched PCR-enzyme-linked minisequence assay. RESULTS: The presence of adenoma component and intramucosal tumor spreading in the ampulloduodenum was significantly higher in intestinal-type tumors (90%, 27 of 30 tumors, and 100%, 30 of 30 tumors, respectively) than in pancreaticobiliary-type tumors (9%, 2 of 22 tumors, and 23%, 5 of 22 tumors, respectively) (P < 0.0001). MUC2 expression was positive in intestinal-type tumors but not in pancreaticobiliary-type tumors. K-ras mutation rates for incomplete intestinal-type tumors (78%, 7 of 9) and metaplastic pancreaticobiliary-type tumors (64%, 7 of 11), which showed MUC5AC (gastric-type apomucin) expression in cytoplasm, were significantly higher than in complete intestinal-type tumors (33%, 6 of 21) and ordinary pancreaticobiliary-type tumors (18%, 2 of 11) (P = 0.01 and P = 0.03, respectively). In pancreaticobiliary-type tumors, K-ras mutation was more frequently recognized in tumors with ampullopancreatic duct tumor extension (75%, 3 of 4) than in those with ampullobiliary duct extension (0%, 0 of 6) (P = 0.01). Furthermore, sequences of K-ras codon 12 were common in 17 carcinomas with adenoma component that were analyzed for both adenoma and carcinoma. CONCLUSIONS: Tumors of the papilla of Vater can be classified histologically as either intestinal type or pancreaticobiliary type, and they have different features according to tumor location, association with adenoma, and MUC2 expression. Furthermore, K-ras mutation is supposed to be associated with tumors arising in the area from the ampulloduodenum to the ampullopancreatic duct, with metaplastic mucus occurring in both intestinal and pancreaticobiliary types.

Adenoma↗
PubMed1999

Acquired immunity in nude mice induced by expression of the IL-2 or IL-4 gene in human pancreatic carcinoma cells and anti-tumor effect generated by in vivo gene transfer using retrovirus.

We have examined the anti-tumor effect in nude mice caused by human pancreatic cancer cells (AsPC-1) modified to secrete IL-2 or IL-4. Loss of tumorigenicity of cytokine-producing, but not wild-type, cells was observed despite their unaltered in vitro proliferation rates; and these anti-tumor effects were dependent on the amount of cytokine released. Wild-type cells inoculated into mice which had rejected IL-2- or IL-4-producer cells showed significant growth retardation, while no retardation was detected when unrelated human colon carcinoma cells were inoculated. Histological examination of regressing IL-2- or IL-4-producing AsPC-1 tumors in nude mice revealed infiltration by CD11b-, but not CD90-, positive cells around the tumors. Treatment of nude mice with anti-asialoGM(1) antibody did not affect loss of tumorigenicity. Mice injected i.p. with IL-2- or IL-4-producing AsPC-1 cells did not die, in contrast to mice inoculated with wild-type cells. Injection of retrovirus-bearing IL-2, but not beta-galactosidase, gene into mice which had wild-type cells in the peritoneal cavity also significantly prolonged survival. Thus, expression of the IL-2 or IL-4 gene in AsPC-1 cells may generate tumor-specific acquired immunity, even in mature T cell-deficient conditions. An anti-tumor response can be induced by in vivo transfer of the IL-2 gene.

Animals↗