Fibrillation induced at powerline current levels.

Electrical fibrillation of the human heart results in many unfortunate deaths. Because little information is available on short duration high current fibrillation, current levels below 1 and 50 A were used to induce ventricular fibrillation in hogs. Application times ranged between 16 ms and 3 s. Fibrillation was only produced when currents were applied during the T-wave period of the cardiac cycle. However, only 50 percent of the current application during the T-wave caused fibrillation. The total body resistance of the hogs was also measured at the high voltages and currents. The average resistance for 90 current applications was 284 omega. Trends in the data show that the total resistance decreases for increasing voltage, for increasing electrode size, and for current applications following the first current application.

Effects of kaolinite on amino acid transport and incorporation into protein by rabbit pulmonary alveolar macrophages.

A study was made of the effects of kaolinite, an aluminum silicate found in cigarette smoke and in alveolar macrophages of cigarette smokers, on the in vitro function of rabbit alveolar macrophages. Macrophages lavaged by standard procedures were incubated as adherent monolayers in the presence or absence of kaolinite, and amino acid incorporation into protein and transport subsequently measured. In the presence of dialyzed serum, kaolinite slightly inhibited incorporation into protein during the first 2 to 3 hr of incubation, after which incorporation ceased and a large percentage of newly synthesized protein was released (50% effect at approximately 0.5 mg/ml kaolinite). A dual-isotope experiment indicated that any change in the synthesis of protein which may have occurred was not selective for any protein or group of proteins. Kaolinite also stimulated noncompetitive amino acid accumulation after 2 to 3 hr in the presence of serum. The effects of kaolinite were immediate when incubations were conducted in the absence of serum. Control experiments showed all of the effects of the aluminum silicate to be on the cells and not on the incubation medium. These results suggest that kaolinite is cytotoxic and exerts its effects by a mechanism similar to that proposed for magnesium silicates and silica, in which the naked silicate is immediately cytotoxic, but if coated with serum protein must first be uncoated by lysozomal enzymes before destroying the cells.

Cigarette smoke components and alveolar macrophage protein synthesis.

A comparison was made of the effects of acrolein and aqueous cigarette smoke extracts on amino acid incorporation into protein by rabbit pulmonary alveolar macrophages. Studies were on cells maintained in vitro as adherent monolayers. Freshly prepared acrolein inhibited amino acid incorporation by significant amounts after approximately 30 min and aqueous smoke extracts after approximately 15 min of incubation. Fifty percent inhibition by acrolein occurred with a dose of 5.5 microgram acrolein/ml, an amount four times that in the amount of aqueous smoke extract required for 50% inhibition according to previously reported findings. Analysis by a dual-isotope technique and sodium dodecyl sulfate polyacrylamide gel electrophoresis showed the inhibitory effect of acrolein to be nonspecific, as had previously been found for aqueous smoke extracts. The presence of the sulfhydryl reagent cysteine, reduced the inhibitory effect of acrolein by 57.5%, but reduced inhibition induced by aqueous smoke extracts by only 12.2%. These results suggest the effects of acrolein are both quantitatively and qualitatively different than those of aqueous smoke extracts.

Protein biosynthesis by the pulmonary alveolar macrophage. Comparison of synthetic activity of suspended cells and cells on surfaces.

An effort to optimize conditions for studying protein biosynthesis by the pulmonary alveolar macrophage in vitro has led to a comparative analysis of the activity of suspended and adherent cells. A number of differences were observed. (1) Suspended cells synthesized protein for only a limited period of time, after which they responded only partially to incubation in fresh medium. This was true even under reincubation conditions in which the cells were allowed to adhere to a surface. Adherent cells, however, synthesized protein during a longer period of time and were fully capable of responding to new medium within the time periods examined. (2) Analyses of the radioactive proteins synthesized using a dual-isotope technique suggested that, during a period of 2 hours, suspended cells synthesized relatively smaller quantities of high molecular weight proteins than adherent cells. (3) The administration of a phagocytic load (zymosan; particle to cell ratio, 10:1) inhibited by 20 per cent the incorporation of isotopic amino acid into protein during a period of 3 hours. The same phagocytic load, however, stimulated incorporation by 20 per cent in adherent cells. (4) The rate of particle uptake measured using oil red O-albumin complexes decreased by approximately 50 per cent in suspended cells preincubated for 2 hours, but was maintained in similarly preincubated adherent cells. It was concluded that pulmonary alveolar macrophages incubated adhered to a surface are more appropriate for metabolic studies than are pulmonary alveolar macrophages incubated in suspension.