Comparative study of a mutant tissue-type plasminogen activator, YM866, with a tissue-type plasminogen activator in a canine model of femoral arterial thrombosis

Because tissue-type plasminogen activator (tPA), used to treat myocardial infarction, has several disadvantages thought to be connected with its low half-life, mutants of tPA have been prepared with longer half-lives. We have compared the thrombolytic effect of such a mutant, YM866, with that of tPA in copper-coil-induced femoral arterial thrombosis in dogs. One hour after thrombus formation, YM866 was administered by intravenous bolus injection, while tPA was given by the same method or by 60-min infusion under adequate heparinization. Both agents exhibited dose-dependent thrombolysis without systemic fibrinogenolysis. The recanalization rate and recanalization time of YM866 by bolus at 0.2 mg kg-1 were, however, equivalent to those of tPA by infusion at 0.4 mg kg-1 (total dose), whereas the recanalization rate of tPA by bolus was low (0.4 mg kg-1). No significant difference in reocclusion rate, reocclusion time, or patency status after successful thrombolysis was seen. These results suggest that YM866 administered at a lower dose by intravenous bolus injection exerted a thrombolytic effect equivalent to that of tPA by infusion, and that heparin could not prevent reocclusion after successful thrombolysis even under adequate anticoagulation.

[Acute myocardial infarct in infants]

A retrospective study was made of 6 children, with nonsurgical-related acute myocardial infarction (AMI), between January 1987 and December 1994. The ratio for gender was 1 and mean age at AMI was 49 days, 4 cases being associated with congenital heart disease (Fallot's tetralogy, truncus arteriosus and DiGeorge syndrome, one case each, and anomalous origin of left coronary artery, 2 cases). Kawasaki disease and coronary embolisation from thrombosis of the renal vein occurred in the other 2 cases respectively. All developed congestive cardiac failure and cardiomegaly. In the ECG pathologic q waves with more than 35 msec occurred in all, and QT prolongation occurred in 3. Five children (83%) all with AMI in the anterior and lateral wall of the left ventricle died, death being related with cardiac mechanical failure and not with arrhythmias.

Synergistic effect of aurintricarboxylic acid and triflavin in a photochemically induced thrombosis model in rats

We report here the synergistic antithrombotic effect of aurintricarboxylic acid in combination with a snake venom-derived disintegrin, triflavin, in a photochemically induced thrombosis model in rats. The time to initiation of thrombus was prolonged by i.v. bolus injection of aurintricarboxylic acid at 10 mg/kg. In contrast, time to occlusion was dose-dependently prolonged by both agents, this prolongation being significant with aurintricarboxylic acid at 10 mg/kg i.v. and with triflavin at more than 3 mg/kg i.v. Interestingly, the combination of aurintricarboxylic acid at 3 mg/kg i.v. and triflavin at 1 mg/kg i.v. prolonged not only the initiation of thrombus, but also the time to occlusion.

Comparison of the antiplatelet agent potential of the whole molecule, F(ab)2 and Fab fragments of humanized anti-GPIIb/IIIa monoclonal antibody in monkeys

1. The potential antiplatelet agent use of the whole molecule, F(ab)2 and Fab fragments of humanized antiglycoprotein (GP) IIb/IIIa monoclonal antibody, hC4G1, were investigated in rhesus monkeys. 2. Fab completely inhibited platelet aggregation 1 hr after an i.v. bolus administration of 1 mg/kg without a decrease in platelet count or prolongation of bleeding time, and the duration of inhibition was much shorter than that of F(ab)2. 3. These results suggest that the Fab fragment of hC4G1 may be a more useful antiplatelet agent in patients with acute thromboembolic diseases than the whole molecule or F(ab)2 fragments.

Antiplatelet and antithrombotic effects of YM337, the Fab fragment of a humanized anti-GPIIb/IIIa monoclonal antibody in monkeys

The antiplatelet and antithrombotic effects of the Fab fragment of the humanized antiplatelet glycoprotein (GP) IIb/IIIa monoclonal antibody C4G1 (YM337) were investigated in monkeys. First, the relationship between the inhibition of platelet aggregation and the prolongation of bleeding time was studied in rhesus monkeys. YM337 dose-dependently inhibited ex vivo platelet aggregation, with complete inhibition at doses higher than 0.25 mg/kg intravenous injection or 1.5 micrograms/kg/min infusion. At 0.25 mg/kg bolus injection followed by 1.5 micrograms/kg/min infusion, YM337 immediately and continuously inhibited platelet aggregation during the 6-h infusion period with platelet aggregation rapidly returning to over 50% of baseline within 1 h after the cessation of infusion. Template-bleeding time was significantly prolonged during the period of complete inhibition of platelet aggregation. Second, the antithrombotic effects of YM337 were investigated in a photochemically-induced thrombosis model in squirrel monkeys. YM337 at a dose of 1 mg/kg intravenous injection followed by 6 micrograms/kg/min infusion for 60 min prevented occlusive thrombus formation in all 4 monkeys. In contrast, time to occlusive thrombus formation did not change on intravenous bolus injection of aspirin 17 mg/kg (11.3 +/- 5.2 min) or sodium ozagrel (9.4 +/- 3.0 min) compared with saline (13.3 +/- 4.0 min). YM337 but not aspirin or sodium ozagrel significantly inhibited ex vivo ADP-induced platelet aggregation, while all drugs completely inhibited arachidonic acid-induced platelet aggregation. However, while aspirin and sodium ozagrel inhibited the thromboxane B2 generation accompanying arachidonic acid-induced platelet aggregation, YM337 had no effect on this variable. Platelet counts and bleeding time showed no significant change in any group in this squirrel monkey model. These results indicate that YM337, with a short half-life, may be a useful therapeutic agent in patients with thrombotic disorders.

Biochemical characterization of a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom

We biochemically characterized a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom. Flavostatin inhibited ADP-, collagen-, and thrombin receptor agonist peptide-induced platelet aggregation in human platelet-rich plasma (IC50 range: 59 to 111 nM) and blocked the binding of biotinylated human fibrinogen to purified GPIIb/IIIa with an inhibitory potency 31,000-fold higher than that of Arg-Gly-Asp-Ser (RGDS). Flavostatin strongly inhibited high-shear-stress-induced platelet aggregation in platelet-rich plasma (PRP) with an IC50 value of 188 nM. Fluorescein isothiocyanate (FITC)-conjugated flavostatin saturably bound to unstimulated and ADP-stimulated washed platelets with high affinity (Kd values: 38 and 21 nM, respectively); the corresponding number of binding sites was 86460 and 79192 per platelet. In competition experiments with several glycoprotein IIb/IIIa antagonists, the binding of FITC-conjugated flavostatin to platelets was completely inhibited by ReoPro, triflavin, TP9201, MK383 and GR144053, but not by YM207, YM337 and B6A3.

Natural antibodies against the immunoglobulin F(ab')2 fragment cause elimination of antigens recognized by the F(ab')2 from the circulation

A humanized monoclonal IgG1 antibody, designated hC4G1, recognizes the fibrinogen receptor glycoprotein (GP)IIb/IIIa on platelets and inhibits platelet aggregation. When the F(ab')2 fragment of hC4G1 (F(ab')2 hC4G1) was administered to cynomolgus monkeys, all the monkeys showed inhibition of platelet aggregation ex vivo. Unexpectedly, a significant decrease in platelet count was observed in 5 of 18 monkeys. Antibodies against F(ab')2 hC4G1 were detected in the plasma of these monkeys by ELISA. Antibody activity in the plasma of these monkeys was significantly correlated with the intensity of platelet decrease (r = 0.84). The natural monkey antibodies to F(ab')2 hC4G1 were directed against the C-terminal region of F(ab')2 fragment common to all human and humanized IgG antibodies. Natural homo-reactive antibodies were also detected in human plasma from 15 of 40 healthy volunteers. Specificity was closely similar to that of the monkey antibodies. Affinity-purified human homoreactive antibodies enhanced phagocytosis of platelets treated with the F(ab')2 hC4G1. Monkey plasma with high homo-reactive antibody activity was confirmed to decrease platelet count when administered together with F(ab')2 hC4G1 to a monkey with low antibody activity. These results suggest that F(ab')2 of humanized and human antibodies causes elimination of the corresponding antigens from the circulation by homo-reactive antibodies.

Tokaracetin, a new platelet antagonist that binds to platelet glycoprotein ib and inhibits von Willebrand factor-dependent shear-induced platelet aggregation

A new platelet antagonist, tokaracetin, was isolated from the venom of Trimeresurus tokarensis by ion-exchange chromatography, heparin-Sepharose chromatography and hydrophobic HPLC. The purified protein showed an apparent molecular mass on SDS/PAGE of 28.9 kDa under non-reducing conditions. On reduction, 16.1 and 15.4 kDa subunits were observed, suggesting that the molecule is a heterodimer. Tokaracetin inhibited the binding of 125I-labelled bovine von Willebrand factor (vWF) and 125I-labelled human vWF in the presence of botrocetin to fixed human platelets. It did not block ADP-, collagen- or thrombin receptor agonist peptide-induced platelet aggregation in human platelet-rich plasma (PRP), or induce platelet agglutination in PRP. On reduction, tokaracetin lost its inhibitory activity on the agglutination of fixed human platelets by bovine vWF. 125I-Tokaracetin specifically bound to washed human platelets with high affinity (Kd 3.9 +/- 1.4 nM) at 47,440 +/- 2780 binding sites per platelet. Binding of tokaracetin to fixed human platelets was reversible, and was inhibited by monoclonal antibody GUR83-35, which is directed against the N-terminal vWF-binding domain of human glycoprotein Ib (GPIb). Tokaracetin completely inhibited vWF-dependent shear-induced platelet aggregation in PRP at 3 micrograms/ml. The N-terminal amino acid sequences of tokaracetin subunits showed a high degree of identity with those of alboaggregin-B. These results suggest that this new platelet antagonist may be a useful tool in the development of specific inhibitors of the vWF-GPIb interaction.

Antithrombotic effect of a humanized anti-GPIIb/IIIa monoclonal antibody, YM207, in a photochemically induced thrombosis model in monkeys

We investigated the antithrombotic effects of a F(ab')2 fragment of a humanized anti-platelet glycoprotein (GP) IIb/IIIa monoclonal antibody, YM207, in a platelet-rich thrombosis model. Thrombus was induced in a mesenteric venule of squirrel monkeys by irradiation with filtered light in combination with i.v. administration of a fluorescent dye (sodium fluorescein). Time to occlusive thrombus formation was significantly prolonged by i.v. bolus injection of 0.3 mg/kg of YM207. At doses of 1 mg/kg and 3 mg/kg, complete occlusion did not occur during 60 min of the observation. Platelet aggregation in platelet-rich plasma was inhibited by YM207 at doses 0.3 mg/kg or more. A good correlation was obtained between inhibition of platelet aggregation and the percentage of GPIIb/IIIa receptors blocked by YM207. Bleeding time was significantly prolonged at a dose of 3 mg/kg. Platelet counts showed no significant change. These results suggest that YM207 is effective in preventing platelet-rich thrombus formation without inducing the prolongation of bleeding time or a significant decrease in platelet count. YM207 may be a useful therapeutic agent for the treatment of thrombotic disorders.

Flavocetin-A and -B, two high molecular mass glycoprotein Ib binding proteins with high affinity purified from Trimeresurus flavoviridis venom, inhibit platelet aggregation at high shear stress

Two high molecular mass proteins, flavocetin-A and flavocetin-B, were purified from Trimeresurus flavoviridis venom. On polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the apparent molecular mass of flavocetin-A and -B were 149 and 139 kDa, respectively, under nonreducing conditions. On reduction, flavocetin-A showed two distinct subunits (17 and 14 kDa), and flavocetin-B three distinct subunits (17, 15 and 14 kDa). At 1 microgram/ml, flavocetin-A and -B (flavocetins) inhibited the von Willebrand factor (vWF)-dependent aggregation of fixed human platelets. However, flavocetins (10 micrograms/ml) had no effect on ADP- and collagen-induced platelet aggregation in PRP. Flavocetins (3 micrograms/ml) also inhibited shear-induced platelet aggregation at high shear stress. Furthermore, flavocetin-A completely inhibited the aggregation of and ATP release from washed platelets stimulated with a low concentration of thrombin. Flavocetin-A specifically bound to platelet with high affinity (Kd = 0.35 +/- 0.13 nM) at 21,500 +/- 1760 binding sites per platelet. The N-terminal amino acid sequences of the subunits of flavocetin-A show a high degree of homology with those of echicetin, botrocetin, alboaggregin-B and factor IX/factor X-binding protein. These results suggest that flavocetins may be a useful tool for further investigation of the GPIb-vWF interaction.

[Restrictive myocardiopathy in children]

Four children, three males and one female, aged 1.5 months to 11 years, with restrictive cardiomyopathy are described. One had patent ductus arteriosus in association. Hepatomegaly, abnormal second heart sound and signs of pulmonary venous congestion in chest X-ray were the most consistent clinical findings. Diagnosis was based on echocardiographic findings, cardiac catheterization data and results of pathology. The most frequent echocardiographic sign was the enlargement of both atria but with the ventricles within normal size and normal systolic function. Abnormalities in second phase of the ventricular filling were recorded in 2D-echo Doppler and cardiac catheterization, where a dip and plateau morphology of ventricular tracings was recorded. Metabolic studies performed in two children were normal, and any child had hypereosinophilia. Two children died, one was lost for follow-up and another is asymptomatic. Remarks on medical and surgical management are made.

[Abnormal origin of left coronary artery from pulmonary artery]

OBJECTIVE

To assess the frequency and severity of the anomalous origin of the left coronary artery (ALCA) from the pulmonary artery (PA).

DESIGN OF THE STUDY

Prospective study of case series between March 1991 and December 1994.

SETTING

Referral-based Paediatric Cardiology Department of a Tertiary Care Center.

PATIENTS AND METHODS

Five consecutive patients (pts) with anomalous origin of the LCA from the PA; there were three infants aged 4 months and two children one 8 year and one 9 year old. There were three girls and two boys. All pts had clinical and 2D-echo and Doppler investigation prior to cardiac catheterization (CC). Indication for CC was based in the association of symptoms and signs of myocarditis or dilated cardiomyopathy of acute or subacute onset and electrocardiographic (ECG) signs of ischemia in infants. In older patients (pts) diagnosis was suspected mainly from ECG. During CC in all pts, aortograms and when necessary selective coronary angiograms were performed. Surgical correction was performed in all children. In two pts stress exercise ECG and stress Thallium studies before and after surgery were performed.

RESULTS

two pts had "adult" an three had "infantile" type of ALCA from the PA. CC was performed and diagnosis was confirmed at surgery in all cases. In one child, correct diagnosis was made by ECO prior to CC and in one case LCA to PA fistula was suspected on Colour-Doppler study. No complications were attributed to CC. Several types of surgery were performed: reimplantation of the ALCA from the PA to the aorta (three pts); tunnel connection of the aorta to the ALCA via the PA (one pt) and left internal mammary to LCA anastomosis (one pt). Two infants died intraoperatively due to extensive myocardial infarction and poor left ventricular function. All the three survivors are asymptomatic after a mean follow up of 34 months. Two oldest pts are currently in New York Heart Association functional class I with normal ECG and improved myocardial perfusion on Thallium scan despite almost total occlusion of LCA at the site of implantation in the aorta as diagnosed on coronary angiogram.

CONCLUSIONS

ALCA from PA is associated with major morbidity and mortality. Diagnosis should be suspected in pts with unexplained myocardial ischemia on ECG and even more if it is associated to clinical signs of dilated cardiomyopathy or myocarditis. Careful assessment on ECO and pulsed Doppler and colour flow mapping should make the diagnosis in most cases. Although surgery can be performed based only on ECO diagnosis, we strongly advise for angiography in all cases as in our experience there are false negative diagnosis by ECO. Preoperative Thallium studies can be useful for the selection of the type of surgery as pts with very little viable myocardium will not survive the establishment of a direct systemic to coronary blood flow and may be candidates for heart transplantation.

Characteristics of binding of [3H]NE-100, a novel sigma-receptor ligand, to guinea-pig brain membranes

We examined the characteristics of binding of radiolabeled N,N-dipropyl-2-[4-methoxy-3-(2-phenyl-ethoxy)phenyl]- ethylamine monohydrochloride ([3H] NE-100), a highly potent and selective sigma-receptor ligand, to guinea-pig brain membranes. [3H]NE-100 showed saturable and reversible binding to sigma binding sites. A dissociation constant (Kd) and maximal numbers of binding sites (Bmax) obtained from Scatchard plot analysis were 1.2 +/- 0.1 nM and 1049.3 +/- 115.1 fmol/mg protein (n = 3), respectively. NE-100 was the most potent inhibitor of [3H]NE-100 binding among several structurally dissimilar sigma-receptor ligands, including haloperidol and (+)-pentazocine. (+)-Benzomorphanes had more than a 10-fold potent inhibitory activity over (-)-benzomorphanes, with regard to [3H]NE-100 binding. The binding of [3H]NE-100 was not influenced by histaminergic, dopaminergic, adrenergic, serotonergic cholinergic or glutaminergic agents at 10(-7) M. GTP-gamma-S and phenytoin also did not affect the binding of [3H]NE-100. A higher [3H]NE-100 binding was observed in the cerebellum and medulla oblongata. Except for the nuclear fraction, the highest level of [3H]NE-100 binding to subcellular fractions was observed in microsomal fractions. These results suggest that NE-100 selectively binds, with a high affinity, to sigma-1 binding sites in guinea-pig brain membranes, as an "antagonist".

Epitopes and biological activities of two monoclonal antibodies to platelet integrin alpha IIb beta 3

We have developed two monoclonal antibodies (MAbs), B6A3 and C4G1. The whole molecules of the two MAbs inhibited in vitro human platelet aggregation induced by either ADP, collagen or thrombin, and their F(ab')2 fragments inhibited ex vivo platelet aggregation induced by ADP in monkey. The concentrations necessary for complete inhibition were 5 and 1 microgram/ml for B6A3 and C4G1, respectively. The Fab fragment of C4G1 but not B6A3 inhibited platelet aggregation. B6A3 and C4G1 bound to activated platelets with dissociation constants of 0.25 and 0.82 nM, respectively. B6A3 recognized an epitope on beta 3, which was sensitive to reduction and alkylation of cystine residues, and C4G1 recognized a conformational epitope on the alpha IIb beta 3 complex, which was sensitive to EDTA. The binding of fibrinogen to activated platelets was inhibited by both MAbs. However, the binding of fibrinogen to isolated alpha IIb beta 3 was inhibited by the whole molecule of C4G1 but not B6A3, although both MAbs bound to the isolated alpha IIb beta 3. The binding of these MAbs to the isolated alpha IIb beta 3 was not inhibited by either Arg Gly Asp Ser (RGDS) or fibrinogen gamma-peptide. In addition, B6A3 but not C4G1 bound to human endothelial cells. These MAbs should contribute to the elucidation of the mechanism of platelet aggregation.

Inhibition by aurintricarboxylic acid of von Willebrand factor binding to platelet GPIb, platelet retention, and thrombus formation in vivo

Commercial aurintricarboxylic acid (ATA) was separated into molecular-weight (MW) fractions of < 210 to > 25,000, using gel permeation chromatography. Fractions with MW > 1,300 effectively inhibited both botrocetin-induced vWF and bovine vWF binding to fixed human platelets. These activities decreased with a MW > 17,000. Platelet retention for a human in vitro was reduced by ATA at 150 microM, as was that for rats ex vivo at 3 mg/kg. ATA prolonged tail transection bleeding time in rats but had only a weak effect on buccal mucosal bleeding time in dogs. ATA had no effect on platelet count but markedly prolonged PTT. ATA at 10 mg/kg exhibited antithrombotic activity and caused a marked improvement in patency status following successful thrombolysis by t-PA in electrically and copper coil-induced thrombosis models. These results suggest that specific inhibitors of the vWF-GPIb interaction such as ATA may prove useful as antithrombotic agents.

Thrombolytic activity of YM866, a novel modified tissue-type plasminogen activator, in a photochemically induced platelet-rich thrombosis model

We compared the thrombolytic activity of a novel modified tissue-type plasminogen activator (t-PA; del 92-173, 275Arg-->Glu), YM866, with that of t-PA in a platelet-rich thrombosis model. Thrombus was induced in guinea pig mesenteric artery by irradiation with filtered light in combination with intravenous (i.v.) administration of fluorescent dye. When occlusion by the thrombus extended to 99% of the luminal area of the vessel, test drug (YM866, t-PA, or saline) was administered by i.v. bolus injection under heparinization. Both YM866 and t-PA exhibited dose-dependent thrombolytic activity; however, the improvement in occlusion rate and the incidence of successful thrombolysis induced by YM866 were three times higher than those induced by t-PA. With YM866 1 mg/kg, alpha 2-plasmin inhibitor levels decreased significantly to 58% of saline group values, but no change was noted in fibrinogen levels. YM866 antigen levels at this dose were seven times higher than those of t-PA. These results suggest that YM866 in single bolus injection is a thrombolytic agent superior to t-PA in platelet-rich thrombi without systemic fibrinolytic activation and that this efficacy is due to the prolonged half-life (t1/2) of the drug.

[The anomalous pulmonary venous connection. A study of 24 children by digital subtraction angiography]

OBJECTIVE

To assess the accuracy of Digital Subtraction Angiography (DSA) in the demonstration of the morphology of Anomalous Pulmonary Venous Connexion (APVC) in children.

DESIGN OF THE STUDY

Prospective study of cases series between January 1989 and July 1992.

SETTING

Referral-based Paediatric Cardiology Department of a Tertiary Care Center.

PATIENTS

Twenty-four consecutive children with anomalous pulmonary venous connection.

METHODS

All pts had clinical and 2D-Echo investigation prior to cardiac catheterization. In all cases selective injections of 0.5 to 1 ml/kg undiluted hypo-osmolar contrast were performed in branch pulmonary arteries and high quality DSA images were recorded. Subtracted images were stored in video and cut films for detailed analysis.

RESULTS

16 pts had total APVC: 11 to Superior Vena Cava (SVC), 2 to Coronary Sinus and 3 to Inferior Vena Cava (IVC). Eight pts had partial APVC: 3 to SVC, 1 to Right Atrium, 3 to IVC (scimitar syndrome), and 1 pt had mixed PAVC. In 8 pts of the whole group, DSA contributed significantly to the final morphologic diagnosis and completed or corrected information obtained by 2D-Echo. In all 18 pts submitted to surgery, the DSA diagnosis was confirmed at operation.

CONCLUSION

DSA is a very useful technique (and even more informative in video images) for anatomic evaluation of pts with APVC and has clear indication when clinical and 2D-Echo findings are not typical.

Determination of nitrite by high-performance liquid chromatography system with electrochemical detector: measurement of nitric oxide synthase activity in rat cerebellum cytosol

A simple and sensitive assay method for NO synthase activity is described. Using glassy carbon as electrode and 30% methanol solution with 10 mM NH4Cl as mobile phase, NO2- can be measured without disturbing ECD-detectable substance in NO synthase assay mixture. The NO2- production in the assay mixture of rat cerebellum: NO synthase increased with protein and in a time-dependent manner. The Km value for the substrate, L-arginine, was 1.25 microM. The enzyme activity was inhibited in a concentration-dependent manner by a NO synthase inhibitor, NNA. The Ki value for NNA was 0.166 +/- 0.060 microM. This ECD-HPLC method for determining NO synthase activity has advantages compared with the diazo-coupling method of the Greiss reagent and the isotopic method in which the conversion of the substrate, [14C]L-arginine, to the product, [14C]L-citrulline is measured; it is simple, sensitive and is convenient for studying the NO synthase activity with various compounds as the substrate.

Thrombolysis with intracoronary administration of YM866, a novel modified tissue-type plasminogen activator, in a canine model of coronary artery thrombosis

We compared the thrombolytic activity of YM866, a novel modified tissue-type plasminogen activator, with that of t-PA by intracoronary administration in a canine thrombosis model of copper coil-induced 6-hr-old thrombi. Either drug was administered by a single injection (10 min) or multiple injection (4 x 10 min) under heparinization (300 IU/kg, i.v.). The reperfusion rate of YM866 was 4 times higher than that of t-PA when administered by single injection. Time to reperfusion of YM866 by single injection was shorter than that of either agent by multiple injection. No group showed any decrease in plasma fibrinogen levels. No acute reocclusion was seen in animals with YM866 by single injection. The improved thrombolytic activity of YM866 by single injection correlated with the relatively higher antigen levels of this agent due to its prolonged biological half-life. These results suggest that single intracoronary administration of YM866 is a safe and effective thrombolytic method for rapid recanalization and lowered acute reocclusion without activation of systemic fibrinolysis.

Thrombolytic activity of a novel modified tissue-type plasminogen activator, YM866, in a canine model of coronary artery thrombosis

The thrombolytic activity of a novel modified t-PA, YM866, was compared with that of a recombinant t-PA in a canine model of copper coil-induced coronary thrombosis. The coronary thrombus was allowed to age for 1, 3 or 6 hr before either drug was administered. YM866 was administered by i.v. bolus injection, while t-PA was given by the same method, as well as by 60-min i.v. infusion. YM866 showed thrombolytic activity 2 to 4 times as potent as that of t-PA when administered by bolus injection, the difference in thrombolytic effect being obvious in the 3- and 6-hr-old thrombi. Coronary reperfusion was achieved more rapidly with YM866 than with i.v. infusion of t-PA. In animals injected with doses of more than 0.1 mg/kg of YM866, no acute reocclusion occurred. Depletion of plasma fibrinogen to 70% of baseline levels was observed in animals given 0.2 mg/kg YM866, 0.4 mg/kg t-PA by bolus, and 0.6 mg/kg t-PA via infusion. The residual plasma YM866 and t-PA antigen 30 min after bolus injection was 25% and 3% of the peak levels, respectively. YM866, administered by i.v. bolus injection, was thus confirmed to exert a thrombolytic effect superior to that of bolus injection and infusion of t-PA, without systemic fibrinolytic activation. These results suggest the potential clinical applicability of YM866 as a thrombolytic agent that can be administered by i.v. bolus injection for acute myocardial infarction.

Binding of [3H]FH-510 to sigma ligand recognition sites in guinea-pig brain membranes

We examined the characteristics of the binding of radiolabeled 5,8-dimethyl-4-(2-di-n-propylaminoethyl)carbazol monohydrochloride ([3H]FH-510), a highly potent and selective sigma ligand, to guinea-pig brain membranes. [3H]FH-510 showed saturable and reversible binding to sigma binding sites. The association rate constant (k+1) and dissociation rate constant (k-1) of [3H]FH-510 were 0.023 min-1.nM-1 and 0.081 min-1, respectively. Scatchard plot analysis showed a dissociation constant (Kd) and maximal number of binding sites (Bmax) of 6.0 +/- 0.63 nM and 1763.3 +/- 177.4 fmol/mg protein (n = 7), respectively. The rank order of potency (Ki) of several structurally dissimilar sigma ligands obtained for the displacement of [3H]FH-510 binding was highly correlated with that determined for [3H](+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ([3H](+)-3-PPP) binding. The binding of [3H]FH-510 was not influenced by histaminergic, dopaminergic, adrenergic, serotonergic or cholinergic agents at 10(-7) M. Higher [3H]FH-510 binding to brain regions was observed in the cerebellum and pons-plus-medulla. Except for the nuclear fraction, the highest level of [3H]FH-510 and [3H](+)-3-PPP binding to subcellular fractions was observed in the microsomal fraction. From these results, it is suggested that FH-510 selectively binds with high affinity to sigma binding sites in guinea-pig membranes.

[Tissue concentration of intravesically instilled (2"R)-4'-o-tetrahydropyranyl-adriamycin or adriamycin in superficial bladder cancer]

Twenty-one patients with superficial bladder cancer entered an analysis of single dose (2'R)-4'-O-tetrahydropyranyladriamycin (THP) or adriamycin (ADM) administration. The patients in each group that have been or not have been treated previously with anti-cancer drugs were randomized into two groups, one was given THP and the other ADM. Thirty-mg of THP or ADM dissolved in 30 ml of physiologic saline was instilled into the bladder, and retained for 1 hour. After 1 hour retention of the drugs, tumor tissues and normal mucosas were removed by punch biopsy forceps transurethrally. The tissue concentrations of THP and ADM were estimated by high performance liquid chromatography. The tissue concentrations of THP and ADM in the tumors were significantly greater (p < 0.05) than those in the normal bladder mucosas. The tissue concentration of THP in the tumors were greater than that of ADM. The tissue concentrations of THP and ADM in the tumor of patients who have been treated with anti-cancer drugs previously were less than those of patients who have not. This results demonstrated that prior therapy with anti-cancer drug may cause a resistance for intravesical instillation chemotherapy. However in patients with prior therapy, the tissue concentration of THP in the tumors were greater than that of ADM. Based on these findings, THP has been shown to be were effective as an intravesical instillating agent especially, in cases with prior chemotherapy.

Sigma receptor modulation of the muscle relaxant action of eperisone

We examined the mechanism of the muscle relaxant action of eperisone, using Straub tail and binding studies. In vivo, eperisone (50 and 100 mg/kg i.p.) produced a dose-dependent inhibition of the Straub tail in mice and this inhibitory effect was significantly reversed by haloperidol (0.5 mg/kg i.p.). This drug in itself had no effect on the Straub tail. Sulpiride (50 mg/kg i.p.) failed to reverse the inhibitory effect of eperisone. In vitro, (+)-3-(3-[3H]hydroxyphenyl)-N-(1-propylpiperidine) ((+)-[3H]3-PPP) specific binding, in rat brain membrane, was prevented by eperisone and the IC50 value was 0.43 nM. The muscle relaxant action of eperisone may be modulated by sigma receptors.

[Left cor triatriatum. Clinical and echocardiographic polymorphism]

Four cases of cor triatriatum in children aged from 4 days to 12 months are described. In one case isolated classical form of the disease occurred, and in the other it was associated respectively to ventricular septal defect, anomalous pulmonary venous connexion and persistence of left superior venae cava. One child had successful surgical correction, two died before surgery could be attempted and one waits operation. Relevant clinical and investigational data are described and the role of echocardiography as an excellent diagnostic tool is stressed. We conclude that isolated form of cor triatriatum can simulate primary lung disease and when associated to other cardiac anomalies it has an earlier diagnosis due to early referral. Surgical results and prognosis depend not only on associated anomalies but also on early diagnosis.