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Biomedical subjects

T Urano

Publications and source records attributed to T Urano.

At least 271 records · Page 15Linked to original sources
PubMed1988

Control of human plasminogen activation.

The activation of Glu1-plasminogen (Glu-Pg) by streptokinase (SK), urokinase (UK) and tissue plasminogen activator (tPA) is under rigorous control by molecules such as epsilon-aminocaproic acid (EACA), fibrinogen (Fg), fibrin (Fn) and, as we have recently discovered, anions. This presentation will focus on the biochemical mechanisms that are involved in these processes. In the case of activation by SK, a species of activator complex, composed of Glu-Pg and SK, can be identified that is inhibited by anions, such as Cl-, and stimulated by Fg and Fn. This species rapidly decays to another activator complex, also consisting of Glu-Pg and SK, that is much less sensitive to control by these effector molecules. The most stable activator complex, containing equimolar SK and plasmin, is not affected to a great extent by anions, Fg or Fn. In the overall activation of Glu-Pg by SK, Cl- behaves as a mixed inhibitor, with a Ki of 6.4-9.2 mM, and Fg functions as a mixed activator, displaying a Ka of 110-240 nM. These results show that activation of Glu-Pg by SK in physiological samples would be considerably inhibited by Cl- in the absence of Fg. The activation of Glu-Pg by both high- and low-molecular weight UK is also inhibited by Cl-, but is stimulated by EACA. The inhibition by Cl- does not occur in the presence of concentrations of EACA that saturate its weak binding sites on Glu-Pg, and the stimulation by EACA is maximally exhibited in the presence of Cl-.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminocaproic Acid↗
PubMed1988

Methylmercury-cysteinylglycine constitutes the main form of methylmercury in rat bile.

The chemical form of methylmercury (MM) in bile was studied by gel filtration and ion exchange chromatography using male rats of various ages. EDTA was added to all mixtures used throughout the experimental procedures in order to prevent oxidation of non-protein sulfhydryl compounds (NPSHs). MM-cysteinylglycine (CysGly) was found to be a predominant chemical form of MM in bile of 4 to 22-week-old rat exposed to methylmercuric chloride. The ratio of MM-glutathione (GSH) tended to increase with age after 4 weeks until 12 weeks of age, reflecting the age-dependent increase in the ratio of GSH to total NPSHs in bile. In 8-week-old rats, although the biliary concentration of GSH was about three times higher than that of CysGly, MM-CysGly was still one of the main chemical forms of MM in bile. This suggests that CysGly has a higher affinity for MM than GSH. In fact, when MM was mixed in vitro with GSH and CysGly in the same molar ratio as that in the bile of 8-week-old rat, MM-CysGly was found to be a predominant mercury-thiol complex. Thus, age-dependent changes in the molar ratio of biliary NPSHs together with their affinity to MM seems to determine the biliary chemical form of MM administered or added into the bile in vitro.

Animals↗
PubMed1988

Species differences in biliary excretion of methylmercury--role of non-protein sulfhydryls in bile.

Species differences in biliary excretion of methylmercury and non-protein sulfhydryls (NPSHs) were studied using male rats, mice, rabbits, guinea pigs and hamsters. EDTA was added to all mixtures used throughout the experimental procedures to prevent oxidation of NPSHs. The rates of mercury excretion into the bile of guinea pigs and rabbits after the administration of methylmercury were significantly lower than those in rats, mice and hamsters. Total NPSH concentrations in the bile of guinea pigs and rabbits analyzed by HPLC were also relatively low compared with those in the other species. These results suggested that NPSH excretion plays an important role in species differences of methylmercury excretion into bile. The chemical form of the methylmercury in the bile was analyzed by gel filtration with Sephadex G-15, and most of methylmercury in bile of all species used in the experiment was bound to low molecular weight substances. The main form of methylmercury in the bile was methylmercury-glutathione (MM-GSH) in mice and hamsters and methylmercury-cysteinylglycine (MM-CysGly) in guinea pigs. Methylmercury in the bile of mice, hamsters and guinea pigs was associated with the main component of NPSHs in bile of the respective species. In the rat bile, however, GSH accounted for a majority (80%) of NPSHs, but methylmercury was separated in two peaks on gel filtration, i.e. MM-CysGly (70%) and MM-GSH (30%). This may be explained by the higher affinity of CysGly to methylmercury than that of GSH. Our data indicate that species differences in the chemical forms of biliary methylmercury reflect the species differences in NPSH components in the bile.

Animals↗
PubMed1987

The control of the urokinase-catalyzed activation of human glutamic acid 1-plasminogen by positive and negative effectors.

The urokinase-catalyzed activation of human Glu1-plasminogen (Glu1Pg) has been found to be inhibited by monovalent anions in the following order of effectiveness: I- greater than SCN- greater than Cl- greater than IO3- greater than HCOO- greater than F- greater than OAc-. The inhibition is reversed by epsilon-aminocaproic acid, with its effectiveness in this capacity generally inversely proportional to the strength of the binding of the anion. The physical basis for the anion inhibition and epsilon-aminocaproic acid stimulation lies in the ability of these effectors to cause measurable opposite alterations in the conformation of Glu1Pg, which are revealed through study of the sedimentation velocity of the protein under various conditions. The kinetic mechanism of the chloride inhibition of Glu1Pg activation has been examined in detail. It has been found that the Glu1Pg.Cl complex serves as an alternate substrate to Glu1Pg for urokinase, with a greatly increased Km (25 +/- 3 and 2.2 +/- 0.3 microM, respectively) for activation. The kcat for the urokinase.Glu1Pg.Cl complex is approximately the same as that for urokinase.Glu1Pg (1.6 +/- 0.2 - 2.0 +/- 0.2/s). Similarly, the stimulation by epsilon-aminocaproic acid also results from effects on the Km of the activation, which is reduced to 1.8 +/- 0.2 microM for the Glu1Pg.Cl.epsilon-aminocaproic acid complex. The kcat for the urokinase.Glu1Pg.Cl.epsilon-aminocaproic acid of 2.4 +/- 0.3/s complex is not greatly different from that for urokinase.Glu1Pg.Cl. Nuclear magnetic resonance studies of the Glu1Pg-induced line broadening of the 35Cl- spectra in the presence and absence of epsilon-aminocaproic acid suggest that Cl- and epsilon-aminocaproic acid simultaneously bind to the protein and that each of these effectors displays its effects through separate binding sites.

Anions↗
PubMed1987

The reciprocal effects of epsilon-aminohexanoic acid and chloride ion on the activation of human [Glu1]plasminogen by human urokinase.

The activation of human [Glu1]plasminogen [( Glu1]Pg) by high-molecular-weight two-chain human urinary urokinase [EC 3.4.21.31) and low-molecular-weight two-chain human urinary urokinase is inhibited by Cl- at physiological concentrations and stimulated by epsilon-aminohexanoic acid (epsilon Ahx; epsilon-aminocaproic acid). The inhibition by Cl- does not occur in the presence of concentrations of epsilon Ahx that saturate the acid's weak binding sites on [Glu1]Pg, and the stimulation by epsilon Ahx is maximally exhibited in the presence of Cl-. We have used intrinsic fluorescence measurements with [Glu1]Pg to show that the conformational alteration and the concomitant increase in activation rate that accompanies epsilon Ahx-binding to [Glu1]Pg in the presence of Cl- does not occur in the same manner without Cl-. Further, the decrease in the intrinsic fluorescence that is attendant to Cl- binding to [Glu1]Pg in the absence of epsilon Ahx is not observed in the presence of this effector molecule. Analyses of the results of this manuscript strongly indicate that a conformation of [Glu1]Pg that is not optimal for its activation by urokinase is adopted in the presence of Cl-, and this is relieved by epsilon Ahx. This has important implications in the inhibition of [Glu1]Pg activation in the solution phase of blood plasma and in the large acceleration of this process when plasminogen is bound to physiological positive effectors via its epsilon Ahx-binding site(s).

Aminocaproates↗
PubMed1987

Cerebral vasodilating and vasospasmolytic action of the cerebral circulation improver 6,7-dimethoxy-1-(3,4-dimethoxybenzyl)-4-([4-(2-methoxyphenyl)-1- piperazinyl]methyl)isoquinoline in experimental animals.

Vasodilating action of a new calmodulin antagonist, 6,7-dimethoxy-1-(3,4-dimethoxybenzyl)-4-([4-(2-methoxyphenyl)- 1-piperazinyl]methyl) isoquinoline (Ro 22-4839), was examined in anesthetized animals. In anesthetized dogs, Ro 22-4839 when given intra-arterially dilated various vessels in the potency order of vertebral greater than internal carotid greater than femoral = coronary much greater than renal vessels. Ro 22-4839 (0.1-1.0 mg/kg i.v.) produced brief increases in the cerebral parietal cortex, vertebral and coronary arterial blood flows more markedly than in femoral, mesenteric and renal arterial blood flows. The compound given intraduodenally decreased the vertebral vascular resistance more extensively than the femoral one in a dose-dependent (3-30 mg/kg) way. The effect of intraduodenal administration was longer-lasting than brief action after intravenous administration, and tended to decrease heart rate. Ro 22-4839 did not significantly change cerebral oxygen consumption regardless of its increase in cerebral oxygen supply, suggesting that its cerebral vasodilating effect was due to its direct relaxing effect on the vascular smooth muscle. Papaverine and ifenprodil produced a shorter-lasting decrease in vertebral vascular resistance and caused significant tachycardia. In the video camera system monitoring the constrictory response of feline pial small vessels of the parietal cortex to hypocapnia, Ro 22-4839 was found to reverse vasoconstriction of both pial arteries and veins at the dose of 0.3 mg/kg i.v./min, which did not dilate these vessels under normocapnia. The compound uniformly reduced the pressor responses to various stimuli (electrical stimulation, norepinephrine and angiotensin II) in pithed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Colonization resistance against Pseudomonas aeruginosa in gnotobiotic mice.

Gnotobiotic (GB) mice were colonized with various groups of intestinal bacteria to determine which members of the indigenous flora would exert colonization resistance against Pseudomonas aeruginosa. P. aeruginosa was cultured from the faeces at levels of 10(3)-10(4) cells/g in GB mice inoculated with either the combination of bacteroides and clostridia obtained from conventional (CV) mice or the combination of bacteroides, lactobacilli and clostridia obtained from limited flora mice. The combination of lactobacilli and clostridia from CV mice also did not eliminate P. aeruginosa from GB mice. However, P. aeruginosa was not detected in the faeces of GB mice by 14 days after inoculation with the combination of bacteroides, lactobacilli and clostridia obtained from CV mice. Thus, a complex indigenous flora consisting of bacteroides, lactobacilli and certain clostridia obtained from CV mice but not clostridia obtained from limited flora mice is required to exert complete colonization resistance against P. aeruginosa in GB mice.

Animals↗
PubMed1986

Purification of rat retinol-binding protein using Blue Sepharose CL-6B.

Studies were conducted to isolate rat plasma retinol-binding protein, the specific transport protein for vitamin A in the rat. Retinol-binding protein was isolated from rat plasma by a new simple procedure using Blue Sepharose CL-6B, and highly purified retinol-binding protein was obtained. This procedure included DEAE-cellulose chromatography at pH 6.0, Sephadex G-75 gel filtration in the presence of 3.0 M urea, Blue Sepharose CL-6B affinity chromatography at pH 7.0 and finally Sephadex G-100 gel filtration at pH 7.4. The third step completely accomplished the dissociation and separation of retinol-binding protein from its complex with prealbumin and plasma albumin. This procedure is a significant improvement over previously published procedures, in which sample recycling and preparative polyacrylamide gel electrophoresis are necessary. The molecular weight, electrophoretic behaviour, ultraviolet and fluorescence spectra of the retinol-binding protein were similar to those appearing in other reports.

Animals↗
PubMed1985

Fibrinogenolysis and fibrinolysis in normal volunteers and patients with thrombosis after infusion of urokinase.

We have studied the effects of urokinase (UK) on concentration changes of alpha 2 antiplasmin (alpha 2 AP) and on fibrino(geno)lysis. Medium dose (480,000 u) or large dose (960,000 u) of UK was given to each of seven normal volunteers by intravenous drip infusion within six hours, and then blood and urine analyses were carried out. Total alpha 2 AP, which includes free alpha 2 AP and alpha 2 AP-plasmin complex, decreased to about 50% of the original value with large dose of UK. alpha 2 AP-plasmin complex appeared in the plasma one hr after UK infusion and increased up to 50% of total alpha 2 AP at the end of UK infusion. B beta peptides, which are liberated from fibrin(ogen) at the very early stage of fibrino(geno)lysis, increased significantly with UK infusion, and was 65 times as much as the normal range at the end of UK infusion. Urinary B beta peptides increased as well as plasma B beta peptides. On the other hand, fibrin(ogen) degradation products (FDP) measured with enzyme immunoassay (EIA) increased only slightly, and moreover, urinary FDP was not detectable at any time. Plasma fibrinogen levels did not decrease and changed within the normal range in both groups. We then gave 960,000 u of UK to four patients with deep vein thrombosis and blood analyses were carried out as with normal volunteers. The most significant observation different from that of normal volunteers was shown in FDP levels. Serum FDP levels of four patients increased significantly in comparison with normal volunteers. Urinary FDP increased as significantly as plasma FDP. In conclusion, the infusion of 960,000 u of UK caused only very early stage of fibrinogenolysis without advanced fibrinogenolysis in normal volunteers, but in thrombotic patients, advanced fibrinolysis was observed.

Fibrinogen↗
PubMed1985

The bursa of Fabricius as a trapping mechanism for environmental antigens.

The bursa of Fabricius was isolated from gut-derived antigens by ligating the bursal duct on the 18th day of incubation. Ligation of the bursal duct (BDL) suppressed the bursal development, spontaneous germinal centre formation in the spleen and the development of serum "natural" agglutinins for bacteria or heteroerythrocytes. Moreover, administration of sterilized cecal contents into the bursal lumen at BDL led to normal level of serum "natural" agglutinins. These findings strongly suggest that the bursa of Fabricius possesses an antigen-dependent process which modulates the development of immune system. Antigen-trapping mechanism of the bursa may supply information about environmental antigens for this process.

Age Factors↗