Combination of prehospital systemic thrombolytic therapy with endovascular procedures in the treatment of patients with acute myocardial infarction

Since July 2002 we have been conducting a study of efficacy of prehospital thrombolytic therapy combined with subsequent endovascular procedures in the treatment of patients with acute myocardial infarction. Fifty nine patients received prehospital fibrinolysis with tissue-type plasminogen activator (TPA, n=28) or streptokinase (n=31) within 6 hours after onset of symptoms. TPA infusion compared with that of streptokinase was associated with smaller ischemic myocardial damage and lower frequency of side effects (3.6 and 38.7%, respectively). Angioplasty or stenting of infarct related arteries were carried out in 47 of these patients. The group of patients subjected to endovascular interventions was characterized by a low rate of in-hospital cardiac events and zero mortality.     

Effect of surfaces on fluid-phase prekallikrein activation

The activation of prekallikrein by factor XII fragments (XIIf), during incubation in plastic tubes was previously noted to be increased by high molecular weight (HMW) kininogen as well as other plasma proteins. In this report, we investigated the mechanism responsible for this increase. Although we confirmed that HMW kininogen, bovine serum albumin, fibrinogen, cold insoluble globulin, and mixed phospholipids apparently increased prekallikrein activation, we found that the product of prekallikrein activation (kallikrein) lost substantial activity in less than 0.5 min after exposure to a variety of fresh surfaces. This loss was partially prevented by the presence of various proteins and phospholipids. Similar protection against inactivation of XIIf, the enzyme in this reaction, was also found. In contrast, no loss of the substrate, prekallikrein, was observed during incubation. The loss of kallikrein activity was found to be proportional to the surface area of the incubation vessel as well as the concentration of kallikrein. Further loss of kallikrein activity could also be prevented by pretreating the vessel with kallikrein. We therefore conclude that various substances apparently affect prekallikrein activation in a purified system by preventing the enzyme and product in the reaction mixture from losing activity due to adsorption to a surface.     

A human antibody binds to alpha-galactose receptors and mimics the effects of Clostridium difficile toxin A in rat colon

BACKGROUND & AIMS: Nearly all human sera contain an immunoglobulin G antibody (antigalactose) that binds the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc expressed on cells from most mammals but not humans. Because the Clostridium difficile toxin A receptor in rodents contains this trisaccharide, the aim of this study was to examine whether antigalactose could mimic the enterotoxic effects of toxin A and bind to receptors containing this trisaccharide. METHODS: Fluid secretion, [3H]-mannitol permeability, and release of rat mast cell protease II and prostaglandin E2 were measured after luminal exposure of rat colon to either purified human anti-galactose, control immunoglobulin G, toxin A, or buffer. RESULTS: Toxin A (5 micrograms) and antigalactose (250 micrograms) but not control immunoglobulin (250 micrograms) stimulated colonic fluid secretion and caused increased mannitol permeability and rat mast cell protease II release. Antigalactose and toxin A and, to a lesser degree, control immunoglobulin G also stimulated release of prostaglandin E2, but only toxin A produced acute inflammation of rat colonic mucosa. Antigalactose and toxin A bound specifically to a single class of colonic brush border receptors with dissociation constants of 10(-6) mol/L and 5.4 x 10(-8) mol/L, respectively. CONCLUSIONS: Fluid secretion, increased permeability, and mast cell activation occur in rat colon when toxin A or human antigalactose immunoglobulin G bind to receptors bearing the trisaccharide Gal alpha 1-3Gal beta 1-4GlcNAc. (Gastroenterology 1996 Jun;110(6):1704-12)     

Fibrinogen biosynthesis in isolated guinea pig megakaryocytes

Fibrinogen synthesis was investigated in guinea pig megakaryocytes. Purified megakaryocytes were incubated with 35S-methionine in methionine-free incubation medium for 18 hours. Newly synthesized fibrinogen in megakaryocyte lysates enriched with purified carrier guinea pig fibrinogen was immunoprecipitated with a specific anti- guinea pig fibrinogen antiserum produced in rabbits. Proteins in the immunoprecipitates were analyzed with a 3.5% to 10.0% gradient polyacrylamide slab gel electrophoresis and auto-radiography. Radioactivity was detected in a protein band of 340,000 daltons. In order to verify fibrinogen synthesis, immunoprecipitate was analyzed by two-dimensional slab gel electrophoresis: (1) the first dimension separated unreduced fibrinogen using a 3.5% to 10.0% gradient gel; (2) following reduction by 2-beta-mercaptoethanol, fibrinogen chains were separated in the second dimension using a 10% gel. Alpha, beta, and gamma fibrinogen chains, which represented carrier guinea pig plasma fibrinogen, were visualized by Coomassie brilliant blue. Autoradiography identified the incorporation of radioactivity into the three fibrinogen chains. In control experiments, immunoprecipitates, produced by exposing megakaryocyte lysates to preimmune rabbit serum and goat anti-rabbit IgG, were also analyzed by the two-dimensional gel system. Radioactivity was not detected in sites corresponding to the migration of fibrinogen subunits. The study demonstrates that isolated guinea pig megakaryocytes can synthesize fibrinogen. The electrophoretic mobility of newly synthesized fibrinogen and subunits is similar to that of guinea pig plasma fibrinogen.     

Correlation of drug sensitivity in vitro with clinical responses in childhood acute myeloid leukemia

Clonogenic cells from 41 children with newly diagnosed acute myeloid leukemia (AML) were tested in vitro for their sensitivity to cytarabine (Ara-C) and daunorubicin (DNR). The findings were then compared with the patients' responses to induction chemotherapy that uniformly included Ara-C and DNR. Light-density marrow cells were incubated with either or both drugs for one hour and cultured over leukocyte feeder layers; clusters and colonies were scored on days 7, 10, and 14. Only the percentage of cell kill in the presence of 1.8 mumol/L DNR was significantly associated with responses to induction therapy: median of 45% (range, 0% to 98%) for patients achieving complete remission v 16% (range, 4% to 23%) for nonresponders (P = .007). The relationship between clonogenic cell kill less than or equal to 23% and clinical responses was striking. Of the 11 evaluable patients with in vitro findings in this category, ten either failed induction therapy or relapsed within 1 year after attaining remission. Kaplan-Meier analysis of relapse-free survival times indicated longer durations of remission for patients whose blast cells showed increased sensitivity in vitro to Ara-C alone, DNR alone, or a combination of the two agents. Seven of 11 patients with cell kills of greater than or equal to 49% in the presence of 1.25 mumol/L Ara-C remain free of leukemia, compared with only one of 12 whose cells were less sensitive to the drug (P = .006). We conclude that the in vitro sensitivity of clonogenic leukemic progenitors to DNR and Ara-C correlates with treatment outcome in children with newly diagnosed AML.     

Role of dust in the working environment in development of chronic bronchitis in British coal miners

Rogan, J. M., Attfield, M. D., Jacobsen, M., Rae, S., Walker, D. D., and Walton, W. H. (1973).British Journal of Industrial Medicine, 30, 217-226. Role of dust in the working environment in development of chronic bronchitis in British coal miners. In the course of a long-term prospective study of chronic respiratory disease in British coal miners the effects on pulmonary ventilatory function of exposure to airborne dust, of simple pneumoconiosis, and of chronic bronchitis have been examined in a group of 3581 coalface workers.

The men were employed in 20 collieries throughout the British coalfields. Their cumulative exposures to coal mine dust in the respirable range (1-5 μm) were calculated from detailed dust sampling results at their work places during a 10-year period and from estimates of earlier exposures based on records of their industrial histories.

A progressive reduction in FEV_1·0 with increasing cumulative exposure to airborne dust has been demonstrated. This effect was evident also in a subgroup of the men studied who reported no signs of mild bronchitic symptoms (cough and phlegm for at least three months in a year).

Among men with pneumoconiosis there was no evidence of a reduction of FEV_1·0 in excess of that attributable to their dust exposures, smoking habits, age, and physique.

Increasing severity of bronchitic symptoms was associated with a loss in FEV_1·0 greater than that expected from the effects of dust exposure as measured, smoking, age, and physique. Possible explanations for this phenomenon are discussed. It is suggested that the results may indicate that once early bronchitic symptoms are present the disease may progress and ventilatory capacity may deteriorate independently of factors initiating the disease process.

     

Radical cations as precursors in the metabolic formation of quinones from benzo[a]pyrene and 6-fluorobenzo[a]pyrene. Fluoro substitution as a probe for one-electron oxidation in aromatic substrates

Three classes of products are formed when benzo[a]pyrene (BP) is metabolized by cytochrome P-450: dihydrodiols, phenols and the quinones, BP 1,6-, 3,6- and 6,12-dione. These products have been thought to arise from attack of a catalytically-activated electrophilic oxygen atom. In this paper we report chemical and biochemical experiments which demonstrate that BP quinones arise from an initial one-electron oxidation of BP to form its radical cation. BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-chlorobenzo[a]pyrene (6-ClBP), and 6-bromobenzo[a]pyrene (6-BrBP) were metabolized by uninduced and 3-methylcholanthrene-induced rat liver microsomes in the presence of NADPH or cumene hydroperoxide (CHP) as cofactor. BP and 6-FBP produced similar metabolic profiles with induced microsomes in the presence of NADPH or 2 mM CHP. With NADPH both compounds produced dihydrodiols, phenols and quinones, whereas with CHP, they yielded only quinones. Metabolism of BP and 6-FBP was also similar with uninduced microsomes and 2 mM CHP, yielding the same BP quinones. With uninduced microsomes in the presence of NADPH, BP produced all three classes of metabolites, whereas 6-FBP afforded only quinones. At a low concentration of CHP (0.10 mM), BP was metabolized to phenols and quinones, whereas 6-FBP gave only quinones. 6-ClBP and 6-BrBP were poor substrates, forming metabolites only with induced microsomes and NADPH. One-electron oxidation of BP by Mn(OAc)3 occurred exclusively at C-6 with predominant formation of 6-acetoxyBP and small amounts of BP quinones. In the one-electron oxidation of 6-FBP by Mn(OAc)3, the major products obtained were 6-acetoxyBP, a mixture of 1,6- and 3,6-diacetoxyBP, and BP quinones. Reaction of BP and 6-FBP radical cation perchlorates with water produced the same BP quinones. Conversely, electrophilic substitution of 6-FBP with bromine or deuterium ion afforded C-1 and/or C-3 derivatives with retention of the fluoro substituent at C-6. These results indicate that metabolic formation of BP quinones from BP and 6-FBP can only derive from their intermediate radical cation.