Biomedical subjects

T Urano

Publications and source records attributed to T Urano.

At least 73 records · Page 4Linked to original sources

PubMed1999

Ral-specific guanine nucleotide exchange factor activity opposes other Ras effectors in PC12 cells by inhibiting neurite outgrowth.

Ras proteins can activate at least three classes of downstream target proteins: Raf kinases, phosphatidylinositol-3 phosphate (PI3) kinase, and Ral-specific guanine nucleotide exchange factors (Ral-GEFs). In NIH 3T3 cells, activated Ral-GEFs contribute to Ras-induced cell proliferation and oncogenic transformation by complementing the activities of Raf and PI3 kinases. In PC12 cells, activated Raf and PI3 kinases mediate Ras-induced cell cycle arrest and differentiation into a neuronal phenotype. Here, we show that in PC12 cells, Ral-GEF activity acts opposite to other Ras effectors. Elevation of Ral-GEF activity induced by transfection of a mutant Ras protein that preferentially activates Ral-GEFs, or by transfection of the catalytic domain of the Ral-GEF Rgr, suppressed cell cycle arrest and neurite outgrowth induced by nerve growth factor (NGF) treatment. In addition, Rgr reduced neurite outgrowth induced by a mutant Ras protein that preferentially activates Raf kinases. Furthermore, inhibition of Ral-GEF activity by expression of a dominant negative Ral mutant accelerated cell cycle arrest and enhanced neurite outgrowth in response to NGF treatment. Ral-GEF activity may function, at least in part, through inhibition of the Rho family GTPases, CDC42 and Rac. In contrast to Ras, which was activated for hours by NGF treatment, Ral was activated for only approximately 20 min. These findings suggest that one function of Ral-GEF signaling induced by NGF is to delay the onset of cell cycle arrest and neurite outgrowth induced by other Ras effectors. They also demonstrate that Ras has the potential to promote both antidifferentiation and prodifferentiation signaling pathways through activation of distinct effector proteins. Thus, in some cell types the ratio of activities among Ras effectors and their temporal regulation may be important determinants for cell fate decisions between proliferation and differentiation.

Animals↗

PubMed1999

Splenic contraction-induced reversible increase in hemoglobin concentration in intermittent hypoxia.

The effect of intermittent hypoxia (IHx) on blood hemoglobin concentration ([Hb]) and the underlying mechanisms were studied in rats exposed to 10% O2, 1 h/day, for up to 5 wk. IHx protocols with longer daily hypoxic exposure show persistent polycythemia; however, it is unknown whether [Hb] increases transiently during hypoxia in protocols without polycythemia. Hypoxia produced a reversible [Hb] increase after 4 days of IHx but not in normoxic controls (NxC) or after shorter period of IHx. Splenectomy abolished the phenomenon. Plasma epinephrine and norepinephrine levels during hypoxia were comparable in IHx and NxC groups, but the epinephrine-induced [Hb] increase was larger in IHx. The alpha1- and alpha2-adrenoreceptor blockade (phentolamine) and alpha2-blockade (yohimbine) abolished the [Hb] increase of IHx rats. Conversely, alpha2-receptor stimulation (oxymetazoline) increased [Hb] during normoxia in IHx but not in NxC. In conclusion, this IHx protocol results in reversible [Hb] increases during hypoxia via splenic contraction mediated by increased alpha2-adrenoreceptor response. This may protect O2 supply during hypoxia without the cardiovascular burden of polycythemia during normoxia.

Adrenergic alpha-1 Receptor Agonists↗

PubMed1999

Effect of chronic sodium cyanate administration on O2 transport and uptake in hypoxic and normoxic exercise.

Systemic O2 transport during maximal exercise at different inspired PO2 (PIO2) values was studied in sodium cyanate-treated (CY) and nontreated (NT) rats. CY rats exhibited increased O2 affinity of Hb (exercise O2 half-saturation pressure of Hb = 27.5 vs. 42.5 Torr), elevated blood Hb concentration, pulmonary hypertension, blunted hypoxic pulmonary vasoconstriction, and normal ventilatory response to exercise. Maximal rate of convective O2 transport was higher and tissue O2 extraction was lower in CY than in NT rats. The relative magnitude of these opposing changes, which determined the net effect of cyanate on maximal O2 uptake (VO2 max), varied at different PIO2: VO2 max (ml. min-1. kg-1) was lower in normoxia (72.8 +/- 1.9 vs. 81. 1 +/- 1.2), the same at 70 Torr PIO2 (55.4 +/- 1.4 vs. 54.1 +/- 1.4), and higher at 55 Torr PIO2 (48 +/- 0.7 vs. 40.4 +/- 1.9) in CY than in NT rats. The beneficial effect of cyanate on VO2 max at 55 Torr PIO2 disappeared when Hb concentration was lowered to normal. It is concluded that the effect of cyanate on VO2 max depends on the relative changes in blood O2 convection and tissue O2 extraction, which vary at different PIO2. Although uptake of O2 by the blood in the lungs is enhanced by cyanate, its release at the tissues is limited, probably because of a reduction in the capillary-to-tissue PO2 diffusion gradient secondary to the increased O2 affinity of Hb.

Animals↗

PubMed1999

Expression of DCC protein in colorectal tumors and its relationship to tumor progression and metastasis.

A loss of heterozygosity (LOH) at the DCC gene locus was detected in colorectal tumors, and this LOH might be related to metastasis. The aim of this study was to determine DCC protein expression in colorectal cancer and to evaluate its prognostic value. Allelic loss of the DCC locus was observed in 16 of the 23 patients (66.7%). In all 16 patients with LOH, DCC expression was decreased in the cancer tissue compared with the adjacent normal mucosa. All 23 colorectal tumors had decreased expression of this protein relative to the adjacent normal colonic mucosa in Western blot analysis. The levels of DCC protein were significantly lower in cancer tissues than in adenoma tissues. Decreased DCC protein expression was also observed by immunohistochemistry in the colorectal cancer cases. There were significant correlations between DCC protein expression and histologic type, venous invasion, and hematogenous metastasis. Patients with DCC-protein-negative tumors had a greater relative risk of recurrence compared with those whose tumors were DCC protein-positive. The 5-year survival rate was 91.0% in patients with DCC-protein-positive tumors, and 58.8% in those with DCC-protein-negative tumors; these differences between the two groups of patients were significant (p < 0.01). In multivariate analysis using the Cox regression model, DCC protein expression emerged as an independent prognostic indicator. These findings suggested that a decrease in DCC expression may have an important role in the progression of colorectal cancers and may be a biologic marker of prognostic significance.

Adenoma↗

PubMed1999

Clinical and immunoregulatory effects of roxithromycin therapy for chronic respiratory tract infection.

The clinical and immunoregulatory effects of long-term macrolide antibiotic therapy for patients with chronic lower respiratory tract infections (CLRTI) were investigated. Clinical parameters and neutrophil chemotactic mediators in the epithelial lining fluid (ELF) of CLRTI patients (n = 10) were examined before and after 3 months oral administration of roxithromycin (RXM). The in vitro effects of RXM were also examined on the release of these mediators from alveolar macrophages (AM) and neutrophils. Arterial oxygen tension (p<0.05), vital capacity (VC) (p<0.001), %VC (p<0.05) and forced expiratory volume in one second (p<0.01) were improved after RXM treatment, but airway bacteria were not eradicated. Among the mediators, the levels of interleukin (IL)-8, neutrophil elastase (NE) and leukotriene B4 (LTB4) were higher in ELF than in plasma of CLRTI patients and they decreased after RXM treatment (n = 7, p<0.05 for each). RXM concentrations were significantly increased in the bronchoalveolar lavage cells of the treated patients. In in vitro experiments, RXM showed inhibitory effects on IL-8 release from AM and neutrophils. In conclusion, interleukin-8, neutrophil elastase and leukotriene B4 contribute to the neutrophilic inflammation in the airways of chronic lower respiratory tract infection patients and the clinical effects of roxithromycin may, in part, be attributable to the suppression of excess release of the chemotactic mediators from inflammatory cells.

Anti-Bacterial Agents↗

PubMed1998

Cancer cells overexpress mRNA of urokinase-type plasminogen activator, its receptor and inhibitors in human non-small-cell lung cancer tissue: analysis by Northern blotting and in situ hybridization.

The transcriptional localizations of urokinase-type plasminogen activator (uPA), its receptor (uPAR) and its inhibitors (PAI-1 and PAI-2), which are possibly involved in cancer metastasis, have not been determined in human lung cancer. To identify their regulation in primary non-small-cell lung cancer, we assayed mRNA levels by Northern blot analysis in 25 cases and determined the localizations of mRNA by in situ hybridization in 10 cases. The amounts of uPA and PAI-2 mRNA were significantly higher in cancerous relative to normal lung tissues. However, no significant difference was observed in uPAR and PAI-1 mRNA levels. All transcripts were present in cancer cells and were predominantly located in tumor edges in several cases. In addition, PAI-1 transcripts were more abundant in poorly and moderately differentiated carcinomas relative to well-differentiated carcinomas and PAI-2 transcripts were more abundant in squamous cell carcinomas than in adenocarcinomas. Thus, PAIs may be involved in modulation of malignant potency. Our results indicate that human non-small-cell lung cancer cells can autonomously express the mRNAs of uPA, uPAR and PAIs, which are possibly involved in metastasis.

Adenocarcinoma↗

PubMed1998

Proteolysis of highly polysialylated NCAM by the tissue plasminogen activator-plasmin system in rats.

Tissue-type plasminogen activator (tPA), a serine protease which converts the zymogen plasminogen to the active protease plasmin, is believed to regulate neurite extension and neural cell migration by modulating extracellular metabolism. The highly polysialylated form of the neural cell adhesion molecule (NCAM-H) is strongly expressed in the developing brain and is believed to play a role in organizing the neural network. In this report, we incubated neonatal rat brain homogenates with human tPA and rat plasminogen in order to determine whether NCAM-H would be degraded. NCAM-H was degraded by plasmin which was formed from rat plasminogen by human tPA. The degradation was inhibited by the addition of plasminogen activator inhibitor type 1 (PAI-1) or aprotinin. These results suggest a possible contribution of the tPA-plasmin system to NCAM-H turnover in the developing brain.

Aging↗

PubMed1998

Effects of electric footshock and water immersion restraint stresses on fibrinolytic parameters in the plasma of rats.

Wistar rats were exposed to electric footshock (ES) or water immersion restraint stress (WS). Blood was taken immediately after, 24, or 48 hours after the stress. The stomachs of rats taken 1 hour after stress application indicate that there were many bleeding spots in the stomachs of WS rats, but practically no visible bleeding spots in the stomachs of ES rats. Plasma levels of t-PA antigens increased in ES rats up to 24 hours after the stress, but the t-PA antigen levels decreased up to 48 hours in ES rats. There were no changes in t-PA activities in plasma of WS rats, but the levels in ES rats decreased immediately and 48 hours after the stress. PAI activity did not change immediately after WS but increased 24 hours after the stress. There was no change in PAI activity in ES rats up to 48 hours. ELT did not change in ES rats, but prolonged in WS rats at 24 hours after the stress. There were significant negative correlations between t-PA antigen levels or activities and ELT in control rats. No correlation was observed in ES or WS rats between t-PA antigen levels and ELT, and no correlation was shown in WS rats between t-PA activities and ELT. Plasma levels of catecholamines increased at the 20-minute period during ES, which may not explain the delayed effects of ES on hemostatic balance. Plasma levels of arginine vasopressin increased significantly immediately after the shock up to 2 hours, indicating that the stress was conveyed to the hypothalamus during the stress application. These results may indicate that some stressors induce an increase or decrease in the local balance of fibrinolytic activities, resulting in bleeding or thrombosis in the local vessels. Such changes may not be detected in the general circulation due to the neutralization of locally induced fibrinolytic changes or the involvement of other hepatically originated hemostatic factors induced by stressors.

Animals↗

PubMed1998

Progressive expansion of hypertensive intracerebral hemorrhage by coagulopathy.

To test the hypothesis that an impaired coagulation system facilitates rapid expansion of hypertensive intracerebral hemorrhage (HICH), coagulation markers were assayed in plasma and their relations to both the hemorrhage size and its progressive expansion were analyzed. Ninety patients with HICH were studied. On admission, plasma samples were taken for the coagulation assay. Hematoma volume was calculated from a computed tomography (CT) scan and its enlargement was estimated by comparison to the volume of the hematoma calculated from a second CT scan taken later within 24 hr. Nine out of 90 patients showed enlargement in their hematoma size (enlarged hematoma group). Four of the enlarged hematoma group fell into acute fatal deterioration and died. Plasma levels of both fibrino peptide A (17.2+/-7.8 vs. 4.0+/-0.6 ng/ml, P < 0.05) and thrombin-antithrombin complex (21.9+/-3.1 vs. 7.4+/-2.8 ng/ml, not significant) were higher in the unchanged group than those in the enlarged hematoma group. In the hematoma-enlarged group fibrino-peptide A level did not exceed 10 ng/ml. In the hematoma unchanged group thrombin-AT-III complex values were positively correlated to hematoma volume. Thus, the coagulation system seemed to be highly activated depending on the hemorrhage volume within three hr after ictus in hypertensive intracerebral hemorrhage patients. When thrombin generation was not sufficient after bleeding, the hematoma seemed to be progressively enlarged. In conclusion, plasma levels of the coagulation markers on admission could be useful predictors of the possible enlargement of hematoma which leads to a poor outcome.

Aged↗

PubMed1998

Nicotine increases stress-induced serotonin release by stimulating nicotinic acetylcholine receptor in rat striatum.

We used a microdialysis technique to analyze the effects of footshock stress on the release of serotonin (5-hydroxytryptamine: 5-HT) in the striatum or prefrontal cortex (PFC) in rats that were pretreated with nicotine. Neither nicotine administration alone nor stress application alone changed 5-HT release. During stress application, however, both chronic nicotine administration and local infusion of nicotine to the striatum significantly increased 5-HT release in the striatum, though not in the PFC. These increases in 5-HT release were eradicated by a local infusion of mecamylamine. Release of 5-HT increased in the striatum during stress application when nicotine was injected to the striatum, while nicotinic injection to the dorsal raphe nucleus did not increase 5-HT release in the striatum. The present study demonstrates that nicotine induced a release of 5-HT upon stress application by stimulating presynaptic nicotinic receptors in the striatum.

Animals↗

PubMed1998

Clinical significance of serum levels of CD44 variant exons 8-10 protein in colorectal cancer.

We examined serum levels of a CD44 splice variant that contained variant exons 8-10 (CD44v8-10) as a tumor marker in colorectal cancer patients. We performed enzyme-linked immunosorbent assays in 81 sera obtained from 71 colorectal cancer patients and 10 healthy controls. Serum CD44v8-10 levels were significantly higher in the colorectal cancer patients than in the healthy controls (0.209 +/- 0.098 versus 0.114 +/- 0.019 OD; P < 0.01). There was a close correlation between immunohistochemical expression and serum CD44v8-10 levels. Surgical resection of the tumors resulted in a reduction of serum CD44v8-10 levels. There was no significant correlation between serum CD44v8-10 level and serosal invasion or histologic type. However, a significant correlation was observed between serum CD44v8-10 level and lymphatic or venous invasion. In addition, serum CD44v8-10 levels were significantly higher in carcinomas associated with lymph node or liver metastasis than in those without metastasis. These findings suggest the usefulness of serum CD44v8-10 level in the prediction of colorectal cancer metastasis.

Biomarkers, Tumor↗

PubMed1998

Cloning and characterization of the murine P2XM receptor gene.

We have isolated the murine counterpart of the human P2XM gene (mP2XM), a P2X purinoceptor that is expressed predominantly in skeletal muscle. The mP2XM gene, consisting of 12 exons that span 10 kb of genomic DNA, encodes a 379-amino-acid product with 83% identity to the human homologue. Two potential transmembrane domains (M1 and M2) are present in the predicted product, and a segment resembling the H5 region of voltage-gated ion channels is completely conserved between human and mouse P2XM proteins. Predominant expression of mP2XM in murine skeletal muscle was confirmed by Northern-blot analysis, and a low level of expression was detectable in lung tissue, although human lung does not express P2XM.

Amino Acid Sequence↗

PubMed1998

Development of maternal IgG-free chick obtained from surgically bursectomized hen.

IgG-free eggs and chicks were developed, so as to study the role of maternal IgG in the development of the immune system. Surgical bursectomy on the 18th day of incubation deprived chickens of B cells and eliminated IgG synthesis. Bursectomized chickens are usually dead before sexual maturity under conventional conditions. When surgically bursectomized chickens were housed in an isolated clean room and antibiotics were administered to them, they could survive to sexual maturity. Finally, we succeeded in obtaining IgG-free fertilized eggs and maternal IgG-free chicks from surgically bursectomized hens. The amount of yolk IgG in IgG-free eggs was one-ten thousandth less than that in normal eggs. The level of IgM in the serum of maternal IgG-free chicks reached six times higher than that of normal chicks 5 days after hatching.

Animals↗

PubMed1998

Extracellular serotonin in the striatum increased after immobilization stress only in the nighttime.

The release of serotonin (5-HT) in the striatum and the motor activity of rats given the immobilization stress were measured using in vivo microdialysis techniques and locomotion counts. Serotonin release in the striatum did not change in the daytime and nighttime, but motor activity in the nighttime was significantly higher than in the daytime. Serotonin release was not significantly increased during immobilization stress in the daytime or nighttime. In the nighttime, however, after the end of stress, 5-HT release was significantly increased from 0.002 ng/dialysate to 0.47 ng/dialysate. The motor activities were also significantly increased after the stress in the nighttime. These results suggest that the effects of immobilization stress on serotonin release in the striatum were different in the daytime and nighttime. In the nighttime, serotonin release in the striatum and the motor activities increased not during but after immobilization stress.

Animals↗

PubMed1998

Severe heat stroke associated with high plasma levels of plasminogen activator inhibitor 1.

In a 38-year-old man, severe heat stroke caused disseminated intravascular coagulation (DIC) associated with significantly elevated plasma plasminogen activator inhibitor 1 levels. Investigation of the effects of hyperthermia on coagulation and fibrinolysis showed, in apparent conflict with previous reports, a time lag between the initial hypercoagulable and hyperfibrinolytic response (within 24 hr) and hypofibrinolysis shown by a disproportionate increase of PAI-1 (after 24 h), which possibly occurs in correspondence with the recovery of vascular endothelial integrity. The patient was discharged without sequelae although computed tomography (CT) scans indicated the likelihood of venous infarction or posterior inferior cerebellar artery area infarction secondary to DIC.

Adult↗

PubMed1998

Effects of nicotine and footshock stress on dopamine release in the striatum and nucleus accumbens.

We have used a microdialysis technique to analyze the effects of nicotine administration on the release of dopamine in the striatum and the nucleus accumbens (NAC) in rats under footshock stress. In the striatum, neither chronic systemic nicotine administration alone nor stress alone changed the extent of dopamine release. During stress application, however, chronic nicotine administration significantly increased dopamine release. In the NAC, stress did not induce increase in dopamine release in rats given nicotine chronically. However, in rats subjected to stress alone, dopamine release in the NAC was significantly increased after stress. In the striatum, the local infusion of 1.0 mM nicotine increased dopamine release. Furthermore, stress significantly increased nicotine-induced dopamine release. The local infusion of 1.0 mM nicotine into the NAC significantly increased dopamine release, but the levels returned to the baseline 30 min later. On the other hand, stress alone induced the release of dopamine 30 min later and the combination of stress and nicotine induced the release of dopamine during the stress and the effects lasted for 30 min. These results suggest that the responses of nicotine-induced dopamine release were different in the striatum and in the NAC under the stress. Stress and nicotine (systematically or locally administered) induced an immediate effect on dopamine release in the striatum, but in the nucleus accumbens stress alone and the combination of stress and nicotine induced a lasting release of dopamine (DA).

Animals↗

PubMed1998

Reduced expression of deleted colorectal carcinoma (DCC) protein in established colon cancers.

Using a bacterial fusion protein, a deleted colorectal carcinoma (DCC)-specific monoclonal antibody (MAb) 127-22 was established. Although MAb 127-22 reacted with almost all normal tissues, it did not react or only weakly reacted with many cancer cell lines, including colonic cancer lines, in flow cytometry. In Western immunoblots, the MAb reacted with a single 190-kDa molecule in a myeloma line Ara-10 extract. This component was scarcely detected in colonic cancer cell lines. Immunoblots of samples from 25 pairs of colonic cancers and adjacent normal tissues and from five adenoma tissues revealed that all normal colonic and adenoma tissues significantly expressed the DCC protein, whereas colonic cancer tissues showed poor expression. These results indicate not only deletion of and lowered mRNA expression of the DCC gene, but also marked reduction of DCC protein occurred in colonic cancer tissues. In addition, colonic cancer patients with liver metastasis expressed significantly lower levels of DCC than those without, suggesting the prognostic value of DCC expression.

Animals↗

PubMed1998

Plasma levels of 5-HT and 5-HIAA increased after intestinal ischemia/reperfusion in rats.

Intestinal ischemia/reperfusion (I/R) causes serious systemic injury, mainly from a variety of bioactive substances released from the injured intestine. To assess the possible roles of serotonin (5-hydroxytryptamine, 5-HT), a bioactive amine mainly stored in the intestine, in I/R injury, we assayed the levels of tryptophan, 5-HT, and 5-hydroxyindole acetic acid (5-HIAA) in the blood and intestine in a rat I/R model. Plasma 5-HT increased significantly over time after reperfusion; the plateau level was obtained 4 h after reperfusion and was associated with an increase in 5-HIAA. Plasma tryptophan levels declined gradually after reperfusion. The ratio of 5-HIAA/5-HT was significantly higher in I/R rats than in control rats, suggesting that elevated 5-HT was quickly metabolized in the systemic circulation. In the intestine, 5-HT decreased dramatically, whereas tryptophan increased. This phenomenon was prominent in the severely damaged intestine. These findings suggest that the injured intestine released large amounts of 5-HT, whereas its synthesis in the injured intestine was suppressed. An increase in 5-HT in the circulation may be related to various circulatory disturbances observed in humans after intestinal ischemia.

5-Methoxytryptamine↗