Captopril lowers coronary venous free radical concentration after direct current cardiac shocks

STUDY OBJECTIVES

Direct current (DC) shocks to the heart cause morphologic and functional myocardial damage. Previous studies have suggested that acute DC shock injury is free radical mediated and that the administration of antioxidant enzymes superoxide dismutase and catalase can reduce the level of DC shock-induced free radicals. Angiotensin-converting enzyme (ACE) inhibitors are clinically used drugs that may scavenge free radicals or reduce free radical generation. The objective of our study was to determine whether the ACE inhibitor captopril lowers free radicals after DC shocks.

DESIGN

In six open-chest dogs, we administered 100-J DC shocks to the epicardium, before and after administration of captopril, 3 mg/kg. We used electron paramagnetic resonance measurements of arterial and coronary venous ascorbate free radical (AFR) as a real-time marker of free radical generation (total oxidative flux).

MEASUREMENTS AND RESULTS

Captopril resulted in a significant lowering of coronary venous AFR concentration: the peak rise in AFR after 100-J shocks was 17.3+/-3.4% (mean +/- SEM before captopril vs. 3.2+/-4.0% after captopril; p<0.05).

CONCLUSIONS

Captopril lowers coronary venous AFR concentration after high-energy epicardial shocks.

Rheolytic thrombectomy with the Possis AngioJet: technical considerations and initial clinical experience

Percutaneous revascularization of thrombus-containing lesions has an increased incidence of adverse events such as abrupt vessel closure, periprocedural myocardial infarction and death. Various pharmacologic and mechanical approaches have demonstrated modest angiographic success with significant periprocedural complications. The AngioJet (Possis Medical, Inc., Minneapolis, Minnesota) is a dual lumen catheter that uses the principle of rheolytic thrombectomy to remove unorganized thrombus. A previously unreported scoring system based on clinical and angiographic data may help to select patients most likely to benefit from AngioJet treatment. When compared with urokinase in the randomized VeGAS 2 Trial, AngioJet therapy yields greater angiographic success with a lower incidence of 30-day major adverse events. Technical considerations and complications are reviewed in detail.

High perimeter impedance defibrillation electrodes reduce skin burns in transthoracic cardioversion

During cardioversion, skin burns result from current preferentially flowing at the electrode edge. We tested new electrodes with high perimeter impedance to yield more uniform current distribution; these electrodes reduced histopathologic skin injury.

Magnesium reduces free radicals in an in vivo coronary occlusion-reperfusion model

OBJECTIVE

This study demonstrated that magnesium (Mg) reduces free radicals after a brief coronary occlusion-reperfusion sequence.

BACKGROUND

Magnesium has been shown to reduce infarct size in patients with acute myocardial infarction. We hypothesized that this action of Mg occurs through its action on free radicals.

METHODS

Eighteen mongrel dogs were studied (nine control, nine receiving Mg). Catheters were placed into the coronary sinus for continuous blood withdrawal. A Varian E-4 electron paramagnetic resonance spectrometer was used to monitor the ascorbate free radical (AFR) signal in the coronary sinus blood; AFR is a measure of total oxidative stress. Occlusion of the left anterior descending coronary artery for 20 min was followed by reperfusion. The study animals received 4 g Mg intravenously starting at 15 min of occlusion (5 min before reperfusion) and continuing during reperfusion.

RESULTS

Results are presented as percent change from baseline +/- SEM. Magnesium blunted the peak AFR increase: at 4 min of reperfusion there was a 4.7 +/- 3.3% increase in AFR signal in the dogs receiving Mg versus an 18.2 +/- 3.3% increase in the control animals (p < 0.05). Total radical flux was reduced during reperfusion by 53% in the Mg dogs compared with controls (p < 0.05).

CONCLUSIONS

Magnesium attenuates AFR increase after an occlusion-reperfusion sequence. To our knowledge this is the first in vivo real-time demonstration of Mg's impact on free radicals.

Transthoracic defibrillation: does electrode adhesive pad position alter transthoracic impedance?

Successful termination of ventricular fibrillation by transthoracic shocks is dependent on achieving adequate current flow, which in turn is governed by transthoracic impedance (TTI). The American Heart Association (AHA) Advanced Cardiac Life Support textbook recommends three electrode positions for defibrillation: (1) anterior-apex, (2) apex-posterior and (3) anterior-posterior. However, there are few data available comparing TTI of these positions. To study this, we applied large (78 cm2) self-adhesive monitor-defibrillator pads to 20 subjects (ten male, ten female, ages 21-79) and measured TTI using a validated test-pulse technique which does not require actual shocks. We performed two studies. In Study 1 (all 20 subjects) the electrode pads were applied in the three positions recommended by the AHA, with the posterior electrode placed in the right infrascapular location. All TTI measurements were made at end-expiration and body surface area (BSA) was recorded. The results (TTI, omega, mean +/- S.D.) for the respective positions were the following: anterior-apex, 82.0+/-24.7; apex-posterior, 71.2+/-23.5; anterior-posterior, 77.0+/-24.7 (P NS). In Study 2 (six subjects) we compared the effect of right vs. left infrascapular posterior electrode placement (TTI, omega): apex-right infrascapular (RIS), 76.8+/-18.4; apex-left infrascapular (LIS), 72.1+/-18.7; anterior-RIS, 72.5+/-19.4; anterior-LIS, 71.6+/-18.6 (P NS). Correlation of TTI (anterior-apex placement) with BSA: TTI = 15.9 (BSA) + 46.7, r = 0.60, P < 0.01; the correlations of TTI and BSA were similar in the other two electrode positions. Thus, the three AHA-recommended electrode positions for transthoracic defibrillation have equivalent and acceptable TTIs; current flow should be similar using any of these positions. Furthermore, the posterior electrode may be placed in either the right or the left infrascapular position without affecting TTI. TTI is related to BSA in any of the three recommended positions; patients with high BSA and TTI may require higher energy selection to achieve defibrillation.

Prevalence and levels of IgG and IgM antibodies against Plasmodium falciparum and P. vivax in blood donors from Rondônia, Brazilian Amazon

Antibodies of IgG and IgM isotypes reacting with Plasmodium falciparum and P. vivax thicksmear antigens were searched for by the indirect fluorescent antibody test (IFAT) in a random sample of 230 blood donors at the transfusion centre of Porto Velho (HEMERON), Rondônia State, western Brazilian Amazon. A high prevalence of IgG seropositivity (32% against P. falciparum, 24% against P. vivax and 37% against either P. falciparum or P. vivax antigens) was detected among them, despite the fact that candidates reporting recent (< 12 months) malaria attacks were not eligible. Only a small proportion of them had also detectable IgM antibodies to these antigens. These data suggest an intense, relatively recent exposure to malaria in such an urban population sample. However, parasitaemia (as detected by microscopical examination of Giemsa-stained thick smears) was patent in only one prospective donor. The antibody profile of blood donors was compared with that of healthy subjects of all age groups, living in a close endemic area (Candeias village, 21 km east of Porto Velho). The villagers were classified into two groups according to their history of a recent (< 12 months) or a remote (> 12 months) past malaria attack due to either P. falciparum or P. vivax. Extensive overlapping was observed when the distribution of antibody titres of healthy subjects from Candeias village with a recent and remote malaria history was compared. In conclusion, subjects with a recent or a remote malaria history could not be distinguished by serological criteria alone.

Auxotrophic mutants of Crithidia fasciculata

In pursuance of genetic studies, after exposure to ethylmethanesulfonate, 11 auxotrophic mutants of Crithidia fasciculata were cloned. Three proved uracil dependent; 3 serine dependent; and the remainder have not had their auxotrophy defined.

Fusion of small unilamellar vesicles induced by a serum albumin fragment of molecular weight 9000

A peptide (P-9) comprising amino acids 307 to 385 of bovine serum albumin induced the fusion of small unilamellar vesicles of phosphatidylcholine at low pH. Upon acidification P-9 exhibited a ultraviolet differential spectrum characteristic of hydrophilic exposure of chromophores. This conformational change, and the structure of P-9 composed of three amphiphilic helixes , suggested a general working hypothesis for the description of protein-induced membrane fusion.

Fusion of small unilamellar vesicles induced by bovine serum albumin fragments

The limited pepsin proteolysis products of bovine serum albumin, fragment A (residues 307-586) and fragment B (residues 1-306), induced the fusion of small unilamellar vesicles of egg phosphatidyl choline at concentrations near 5 microM. Fusion was demonstrated and analyzed on the basis of: a) time-dependent changes in absorbance; b) dilution of the fluorescent label 2-(10-(1-pyrene)decanoyl) phosphatidyl choline, incorporated into a small percentage of the vesicles, as measured by the decrease in the excimer to monomer (E/M) ratio; c) increase of the average hydrodynamic radius of the liposomes, estimated by Sepharose 4B filtration, and d) the strict inverse relationship between the size of the liposomes and their E/M ratios. Albumin fragment B, like albumin, induced the formation of large aggregates in which rapid cooperative fusion produced vesicles having a large hydrodynamic radius. Fragment A did not produce large aggregates and the initial fusion products exhibited a hydrodynamic radius. Fragment A did not produce large aggregates and the initial fusion products exhibited a hydrodynamic radius smaller than those obtained with fragment B. Albumin and fragments A and B are fusogenic only at pH below 4.0. These data discussed in terms of a general model for a signal-dependent protein-induced membrane fusion.

The use of pluronic polyols in the precipitation of plasma proteins and its application in the preparation of plasma derivatives

Pluronic F-38 was used a precipitant of plasma proteins under varying conditions of pH and polymer concentration. Results indicated that marked differences in the solubility of the plasma proteins in F-38 solutions can be appled to the separation of plasma components. The feasibility of the industrial application of this fractionation method was tested in several experiments. Conditions were established for the preparation of albumin, human plasma protein fraction (HPPF), and immune serum globulin (ISG) with similar yield and purity as those prepared by the Cohn methods. Current procedures for the preparation of antihemophilic A (Facor VIII) concentrate and prothrombin complex (Factors II, VII, IX, and X) were adapted to the F-38 process by removal of the clotting factors from the starting plasma prior to polymer precipitation. In addition, a plasma protein solution free of lipoproteins, isoagglutinins, and clotting factors was developed which has proven useful as a perfusion medium in organ preservation.

A new method for isolating the nonidentical protein subunits of human plasma alpha-lipoprotein

Human plasma alpha lipoprotein (alphaLP) was totally delipidated by gel filtration on Sephadex LH-20 in a medium of 2 butanol:acetic acid:H(2)O, 4:1:5. The resulting alpha protein (alphaP) exhibited two major bands, labeled C and D, on acrylamide-gel electrophoresis in 5.0 M urea at pH 8.8 or 4.0. Minor bands labeled A and B, also present, were shown to be aggregates of C which form when the latter is lyophilized. The C and D components were isolated in pure form from alphaP (prepared by LH-20 chromatography of alphaLP) by gel filtration of this protein on Sephadex G-200 in a medium of 1.0 N acetic acid: the C component emerged with a distribution coefficient (K(d)) of 0.4, and the D component with a coefficient of 0.7. From each 100 mg of alphaP, 68 mg of C and 22 mg of D were isolated. 3 mg of a minor fraction with K(d) 0.1, containing A and B components as well as C, were also obtained. D but not C reacts with rabbit antiserum to human alphaLP. C and D differ substantially in content of arginine, histidine, (1/2)-cystine, isoleucine, and tryptophan.