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T Imai

Publications and source records attributed to T Imai.

At least 703 records · Page 39Linked to original sources
PubMed1992

[Vitreous oxygen tension of proliferative diabetic retinopathy].

The authors investigated the vitreous oxygen tension in 30 eyes of 29 cases of proliferative diabetic retinopathy patients in order to determine the distribution of oxygen tension and the possible role of neovascular tissue in tissue oxygenation. Vitreous oxygen tension was measured using a polarographic oxygen electrode and a PO2 monitoring system (PO-2080). Prior to pars plana vitrectomy, the oxygen electrode was inserted into the vitreous cavity under microscopic observation with dim illumination transmitted fiberoptically. The respective oxygen tension at the mid-vitreous cavity, above the optic disc, above the macula, above the neovascular tissue, in the peripheral vitreous, above the photocoagulated retina and above the non-photocoagulated retina were 15.8 +/- 4.7 mmHg, 31.2 +/- 10.0 mmHg, 17.1 +/- 4.0 mmHg, 32.0 +/- 9.9 mmHg, 15.6 +/- 5.1 mmHg, 16.5 +/- 5.5 mmHg and 18.6 +/- 4.9 mmHg. The oxygen tension values above the neovascular tissue and above the optic disc showed statistically significantly higher values than that of midvitreous cavity. We assume this to be due to differences between the oxygen demand and supply on the neovascular tissue, because in these tissues there are large amounts of vessels and blood flow compared to oxygen consumption. Therefore residual oxygen causes oxygen flow from the neovascularization to the mid-vitreous. This outcome is one of the facts which supports the hypothesis that neovascular tissues develop in order to compensate for retinal ischemia by releasing oxygen.

Adult↗
PubMed1991

Simultaneous determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolite in dog plasma by high-performance liquid chromatography with electrochemical detection.

A rapid and sensitive high-performance liquid chromatographic analysis, with electrochemical detection, has been developed for the simultaneous determination of a new calcium-channel antagonist, (+/-)-methyl 2-oxopropyl-1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedi carboxylate (I, MPC-1304), and its active metabolite in dog plasma. The plasma extract with toluene was chromatographed on a reversed-phase column and detected by an electrochemical detector at + 0.92 V. Calibration curves were linear from 2.0 to 100.0 ng/ml, and the detection limit was ca. 0.25 ng/ml. This method is applicable to the simultaneous determination of I and its metabolite in dog plasma following the oral administration of I.

Animals↗
PubMed1991

Interleukin-6 supports human megakaryocytic proliferation and differentiation in vitro.

The effect of interleukin-6 (IL-6) on cells of human megakaryocyte (MK) lineage from cord blood was explored. In semisolid colony assays containing human plasma, a greater number of both MK colonies and cells per colony was seen in the presence of IL-6 and IL-3 than in the presence of IL-3 alone. This stimulatory effect of IL-6, observed on both small and large MK colonies, was completely eliminated by the addition of anti-IL-6 antibody to the culture. IL-6 alone had no effect on MK colony formation. In the primary culture, MKs showed larger cell size and DNA content in the presence of both IL-3 and IL-6 than IL-3 alone. The replating experiments using immature MKs grown in the presence of IL-3 showed that IL-6 significantly augmented both cell size and DNA content. This effect was also neutralized by an anti-IL-6 antibody. IL-3 had no tangible effect on MK differentiation. Synergism between IL-6 and IL-3 on MK differentiation was not confirmed. These results suggest that IL-6 is a synergistic factor in the proliferation of MK progenitors and a direct effector of differentiation of immature MKs on in vitro human megakaryocytopoiesis.

Cell Differentiation↗
PubMed1991

Monosynaptic excitation of motoneurons innervating forelimb muscles following stimulation of the red nucleus in cats.

We examined the rubrospinal projection to forelimb motoneurons (Mns) in cats, in comparison with the corticospinal projection. Under pentobarbital anesthesia, intracellular recordings were made from forelimb Mns following stimulation of the red nucleus (RN) and the cerebral peduncle (CP). Single pulse stimulation of the RN produced excitatory postsynaptic potentials (EPSPs) in the majority of forelimb Mns (58/80, 72%). Segmental latencies of RN-EPSPs were shorter than 1.2 ms in 14 out of 22 Mns in which RN-EPSPs were detected in the C8-T1 segments, and in 3 of 36 Mns in the C6-C7 segments. The results suggest monosynaptic rubro-motoneuronal connections in a substantial portion of forelimb Mns particularly in the C8-T1 segments. There was no evidence suggesting monosynaptic connections between cerebral cortex and forelimb Mns.

Animals↗
PubMed1991

Localization of metallothionein in nuclei of growing primary cultured adult rat hepatocytes.

In primary cultured adult rat hepatocytes stimulated by epidermal growth factor and insulin, dramatic changes in the subcellular distribution of metallothionein were clarified by indirect immunofluorescence using antisera specific for this protein. Metallothionein was detected only in the cytoplasm of cultured hepatocytes in the G0 and G1 phases, but was concentrated in the cell nuclei in the early S phase. The strongest staining pattern in the nuclei was observed 12 h after stimulation. Subsequently, the intensity of metallothionein staining in the nuclei decreased. These results suggest that primary cultured hepatocytes are suitable for examining the relation between subcellular localization of metallothionein and cell growth.

Animals↗
PubMed1991

Endothelin-3 stimulates production of endothelium-derived nitric oxide via phosphoinositide breakdown.

Cultured bovine endothelial cells (EC) have specific receptors for endothelin (ET)-3 functionally coupled to phosphoinositide breakdown. We studied whether ET-3 stimulates synthesis of nitric oxide (NO), an endothelium-derived relaxing factor that activates soluble guanylate cyclase in EC, and whether the ET-3-induced NO formation involves G-proteins. ET-3 dose-dependently stimulated production of intracellular cGMP in EC, of which effects were abolished by pretreatment with NG-monomethyl L-arginine, an inhibitor of NO synthesis, and methylene blue, an inhibitor of soluble guanylate cyclase. The stimulatory effects of ET-3 on cGMP production, inositol trisphosphate formation and increase in cytosolic free Ca2+ concentration were similarly blocked by pretreatment with pertussis toxin (PTX). These data suggest that ET-3 induces synthesis of NO mediated by phosphoinositide breakdown via PTX-sensitive G-protein in EC.

Animals↗
PubMed1991

Analysis of two-dimensional electrophoretic patterns of proteins obtained from the sera of normal and tumor-bearing nude rats.

To classify two-dimensional electrophoresis (2-DE) patterns of normal and abnormal samples, a new parameter, named shift value, is introduced. The shift value is defined by the product of three indices; differences in density, differences in area, and the Euclid distance between peaks of matched glycoprotein spots in the 2-DE patterns. Shift values obtained from the differences between the 2-DE patterns of tumor-bearing and normal sera (control) were always found to be larger than those obtained from two control patterns. The shift value obtained from glycoprotein spots could be more effectively used to distinguish normal and abnormal patterns than that obtained from simple proteins. In our earlier attempts to compare serum proteins of normal and tumor patients, we could not discriminate differences caused by genetic background. In order to circumvent this difficulty, we employed an inbred strain of nude rats into which various types of human cancer had been implanted. Reliability of the analysis is enhanced by using a polyacrylamide gel backed with a silanized glass support and an automatic 2-DE apparatus.

Animals↗
PubMed1991

Physical map of the 3' region of the human immunoglobulin heavy chain locus: clustering of autoantibody-related variable segments in one haplotype.

We have constructed the physical map of the 3' region of the human immunoglobulin heavy chain variable region (VH) genes. DNA segments extending to 200 kb upstream of the JH segment were isolated in two YAC clones. Five VH segments were identified in this region in the 5' to 3' order, V(II-5), V(IV-4), V(I-3), V(I-2), and V(VI-1) segments which were all structurally normal and orientated in the same direction as the JH segments. From DNA of a different cell line we have isolated a cosmid contig containing the same DNA region which has extraordinary polymorphism. The YAC and cosmid DNAs were called haplotypes A and B, respectively. Haplotype B contained an additional VH-I segment (V(I-4.1b)) between the V(II-5) and V(IV-4) segments. V(I-4.1b) segment is almost identical to a previously published VH sequence encoding a rheumatoid factor. Another VH segment in the B haplotype (V(I-3b)) corresponding to the V(I-3) segment also showed 99.7% nucleotide sequence homology with an anti-DNA autoantibody VH sequence. However, none of the VH sequences in haplotype A showed such strong homology with autoantibody VH sequences. The results suggest that VH haplotypes may have linkage with autoantibody production.

Amino Acid Sequence↗
PubMed1991

Enhancement of dissolution and absorption of mefenamic acid by egg albumin.

The dissolution behavior and absorption of mefenamic acid following oral and rectal administration from drug:egg albumin solid dispersions have been studied in comparison with those of the drug alone. The interaction of drug with egg albumin in aqueous solution and solid state were examined by solubility analysis, dialysis experiments, and X-ray diffractometry. The results showed that the dissolution rate of mefenamic acid, and also the release of drug from witepsol H-15 suppositories, were significantly increased by using egg albumin:drug solid dispersions. Although egg albumin:drug solid dispersion enhanced the mean serum levels and the area under serum concentration-time curves after oral and rectal administration compared with those of the drug alone, no significant differences were found between the mean residence time values of drug and its solid dispersion. It was also noted that the extent of bioavailability of mefenamic acid and its solid dispersion following oral administration was significantly greater than that following rectal administration.

Administration, Rectal↗
PubMed1991

E1A gene products stimulate in vitro transcription from the adenovirus early region 4 promoter by enhancing a stable preinitiation complex.

A cell-free transcription system using nuclear extracts prepared from adenovirus type 5 (Ad5)-infected and mock-infected cells were utilized to study the E1A-mediated transactivation of transcription from the Ad5 early region 4 (E4) promoter. The transcription activity of Ad-infected cell extracts was several times higher than that of mock-infected cell extracts when the E4 wild-type (WT) promoter was used. The increased activity required expression of E1A proteins. However, the transcription activities of both cell extracts were not different when the mutant promoter containing only the E4 TATA box was used. The formation of a stable preinitiation complex at the E4 WT promoter was facilitated by expression of E1A, whereas it was not facilitated at the mutant promoter. The results suggested that the E1A proteins stimulated transcription from the E4 promoter by enhancing the formation of a stable preinitiation complex through the upstream elements, together with the TATA box.

Adenovirus Early Proteins↗
PubMed1991

Fibrolamellar carcinoma of the liver--a case report.

A 36-year-old woman was admitted to our hospital because of general fatigue. The physical and laboratory findings on admission revealed splenomegaly, pancytopenia, hypocoagulopathy, liver hypofunction with a hepaplastin test of 55% and ICG Rmax of 0.6 mg/kg/min. Diagnostic imaging showed a hypoechoic mass 1.5 in diameter a low density area on the CT scan and a faint tumor stain on the AAG in the posterior inferior area of the liver. On a diagnosis of hepatocellular carcinoma with liver cirrhosis and hypersplenism, partial hepatectomy and splenectomy were performed. The resected hepatic specimen revealed a small liver cancer of 1.9 x 1.5 x 1.3 cm with liver cirrhosis. The specimen consisted of a firm rubbery mass. Macroscopically, the tumor appeared oval and was lobulated with a thin capsule. A fibrous scar was observed in the central area. Microscopically, malignant hepatocytes showed various shapes, ranging from polygonal to spindle form, with eosinophilic granular cytoplasm and were surrounded by abundant fibrous stroma. Orcein stain, revealed that these malignant hepatocytes contained many black granules of copper-binding protein. Immunoperoxidase staining for alpha 1-antitrypsin was also positive in the malignant hepatocytes. However, within this lamellar fibrous regions, there were many cords of tumor cells in which nucleoli were absent and abortive biliary differentiation was suggested. Consequently this tumor was diagnosed as an atypical fibrolamellar hepatocellular carcinoma. We think that this case is the 3rd case reported in Japan and the 2nd case in a Japanese person.

Adult↗
PubMed1991

Comparative effects of diet or glibenclamide on insulin secretion and action in non-obese NIDDM.

We compared the effects of dietary treatment (D) and diet plus glibenclamide (DPG), for 3 weeks, on glycemia, insulin secretion and action in 2 groups of non-obese patients with NIDDM matched for fasting plasma glucose level. Fasting glycemia decreased in both groups with greater reductions after DPG (n = 7, 10.0 +/- 0.6 to 6.3 + 0.3 mmol/l, M +/- SEM, P less than 0.02) than after D (n = 7, 10.1 +/- 0.8 to 8.7 +/- 0.7 mmol/l, M +/- SEM, P less than 0.02). The magnitude of day-time elevation of plasma glucose over the fasting level, however, was reduced only after DPG. DPG but not D improved the plasma insulin response to glucose ingestion and in vivo insulin action measured by insulin tolerance test with unaltered erythrocyte 125I-insulin binding. This might indicate potentiation of insulin action at post-receptor binding steps. Improvements in in vivo insulin action and in insulin secretion after DPG closely correlated with decrease in fasting glycemia and reduction in the day-time elevation of plasma glucose levels, respectively. In conclusion, diet improved glycemic control in non-obese patients with NIDDM mainly by reducing fasting glycemia, although the mechanism remains unknown. Glibenclamide added to the diet further decreased fasting glycemia by improving in vivo insulin action and reduced the magnitude of day-time elevation of plasma glucose by enhancing endogenous insulin secretion.

Blood Glucose↗
PubMed1991

Improvement of absorption rate of indomethacin and reduction of stomach irritation by alginate dispersions.

The dissolution rates of indomethacin from low molecular weight (mol. wt) alginate dispersions were significantly enhanced in comparison with that of indomethacin alone. The dispersion with lower mol. wt alginate exhibited more rapid dissolution rate than that of dispersion with higher mol. wt alginate. These enhanced dissolution rates of indomethacin by alginate may be due to the improvement of wettability and the decrease of crystallinity and crystal size. The absorption rate from alginate dispersions was enhanced in comparison with that from indomethacin alone, and enhanced only the rate of bioavailability in beagle dogs and volunteers. In addition, indomethacin-induced gastric lesions were reduced by dispersing indomethacin in alginate.

Administration, Oral↗
PubMed1991

Lack of correlation between P pulmonale and right atrial overload in chronic obstructive airways disease.

The correlation between P pulmonale and right atrial overload in chronic lung disease was studied. Right atrial pressure, pulmonary artery pressure, and cardiac output were measured with a Swan-Ganz catheter in nine patients with chronic lung disease and P pulmonale on the electrocardiogram (P wave amplitude of greater than or equal to 2.5 mm (0.25 mV) in leads II, III, and a VF. The results were compared with those in six patients with an atrial septal defect (left to right shunt greater than or equal to 50%) and six patients with pulmonary hypertension (mean pressure greater than or equal to 30 mm Hg without left sided heart disease). Right atrial volume and wall thickness were measured in 10 cases of P pulmonale among 1000 necropsy cases and compared with 141 normal hearts from the same series. The patients with P pulmonale did not show a significant increase in right atrial or pulmonary artery pressures. None of the patients with an atrial septal defect or pulmonary hypertension had P pulmonale on the electrocardiogram. In the necropsy cases of P pulmonale mean (1 SD) in right atrial volume (32 (12) ml) and wall thickness (1.5 (0.7) mm) were not significantly increased (40 (14) ml and 1.4 (0.5) mm in the normal hearts). There was a significant inverse relation between the presence of P pulmonale and the cardiothoracic ratio. In all the patients with P pulmonale chest x ray showed a low cardiothoracic ratio, a considerably depressed diaphragm, and a pendulous heart. This study showed no correlation between P pulmonale and right atrial overload in chronic lung disease. A more vertical anatomical position of the heart, particularly of the right atrium, seems to be the major factor responsible for generation of P pulmonale in chronic airways disease.

Aged↗
PubMed1991

Mast cell heterogeneity: protein composition, biosynthesis and mRNA characterization.

Proteins of rat peritoneal mast cells (PMC), rat intestinal mast cells (IMMC) and human skin mast cells (SMC) were compared by two-dimensional electrophoresis. PMC and IMMC had many similarities in distribution of their neutral/acidic proteins but marked differences in the more abundant, granule-associated basic proteins. SMC proteins showed a unique distribution. Distributions of the products of in vitro translation of PMC and IMMC RNA were different from those of proteins isolated directly from these cells which, together with results of pulse-chase labelling experiments, shows evidence for processing of certain mast cell proteins including rat mast cell proteases I and II.

Humans↗
PubMed1991

Cellular mechanism of endothelin-1 release by angiotensin and vasopressin.

Release of endothelin-1, a novel potent vasoconstrictor peptide originally isolated from endothelial cells, from cultured bovine endothelial cells has been shown to be stimulated by arginine vasopressin and angiotensin II. To elucidate the cellular mechanism by which endothelin-1 is released by these vasoconstrictors, we tested the effects of several compounds on the agonist-induced endothelin-1 release and studied the changes of cytosolic free Ca2+ concentrations and phosphoinositide breakdown by these agonists in cultured bovine endothelial cells. Protein kinase C inhibitors (H-7, staurosporine), an intracellular Ca2+ chelator, and an inhibitor of phospholipase C (neomycin), all abolished the agonist-induced endothelin-1 release, whereas the Ca2+ channel blocker nicardipine was ineffective. Although synthetic 1,2-diglyceride (diolein) dose dependently stimulated endothelin-1 release, downregulation of protein kinase C after pretreatment with phorbol ester resulted in decreased effects to increase endothelin-1 release by the agonists. Both arginine vasopressin and angiotensin II induced immediate and transient increases in intracellular Ca2+ levels of fura-2-loaded endothelial cells as well as formation of inositol trisphosphate; the agonist-induced intracellular Ca2+ increases were not affected either by nicardipine or by chelating extracellular Ca2+. The arginine vasopressin- and angiotensin II-induced intracellular Ca2+ increases, inositol trisphosphate formation, and endothelin-1 release were completely abolished by V1-receptor antagonist and saralasin, respectively. It is concluded that arginine vasopressin and angiotensin II stimulate the release of endothelin-1 by a common mechanism, involving receptor-mediated mobilization of intracellular Ca2+ and activation of protein kinase C in endothelial cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Endothelin-1 is an autocrine/paracrine growth factor for human cancer cell lines.

We studied whether a novel vasoconstrictor peptide, endothelin-1 (ET-1), is synthesized by and released from human carcinoma cell lines, and whether ET-1 stimulates proliferation of these tumor cells. ET-1-like immunoreactivity was released from both HeLa and HEp-2 cells as a function of time. Reverse-phase HPLC of the conditioned media from HeLa cells revealed a major peak coeluting with standard ET-1. Northern blot analysis demonstrated the expression of mRNA for ET-1 precursor in both tumor cell lines. Both cell lines contained a single class of specific binding sites for ET-1. ET-1 dose-dependently induced increases in cytosolic free Ca2+ concentration in fura-2-loaded tumor cells, whose effect was completely abolished by chelating extracellular Ca2+ or by Ca(2+)-channel blocker. ET-1 stimulated proliferation of the quiescent cell lines in a dose-dependent manner, whose effect was inhibited by Ca(2+)-channel blocker. Polyclonal antibody for ET-1 inhibited proliferation of these cell lines, whereas nonimmune serum had no effect. These results demonstrate that ET-1 is synthesized by and released from human epithelial carcinoma cell lines, and that exogenous and endogenous ET-1 stimulates proliferation of the cells possibly through Ca2+ influx, suggesting its role as an autocrine/paracrine growth factor for certain tumor cells.

Calcium↗