Artificial Space Weathering to Mimic Solar Wind Enhances the Toxicity of Lunar Dust Simulants in Human Lung Cells.

During NASA's Apollo missions, inhalation of dust particles from lunar regolith was identified as a potential occupational hazard for astronauts. These fine particles adhered tightly to spacesuits and were unavoidably brought into the living areas of the spacecraft. Apollo astronauts reported that exposure to the dust caused intense respiratory and ocular irritation. This problem is a potential challenge for the Artemis Program, which aims to return humans to the Moon for extended stays in this decade. Since lunar dust is "weathered" by space radiation, solar wind, and the incessant bombardment of micrometeorites, we investigated whether treatment of lunar regolith simulants to mimic space weathering enhanced their toxicity. Two such simulants were employed in this research, Lunar Mare Simulant-1 (LMS-1), and Lunar Highlands Simulant-1 (LHS-1), which were added to cultures of human lung epithelial cells (A549) to simulate lung exposure to the dusts. In addition to pulverization, previously shown to increase dust toxicity sharply, the simulants were exposed to hydrogen gas at high temperature as a proxy for solar wind exposure. This treatment further increased the toxicity of both simulants, as measured by the disruption of mitochondrial function, and damage to DNA both in mitochondria and in the nucleus. By testing the effects of supplementing the cells with an antioxidant (N-acetylcysteine), we showed that a substantial component of this toxicity arises from free radicals. It remains to be determined to what extent the radicals arise from the dust itself, as opposed to their active generation by inflammatory processes in the treated cells.

Lymphocytic responses to streptococcal antigens in glomerulonephritic patients.

The lymphocytes from patients with progressive glomerulonephritis showed significant inhibition of cell migration in the presence of group A streptococcal particulate antigens. Marked increases in the level of DNA synthesis of these lymphocytes were also observed after contact with these antigens. Lymphocytes from patients with unrelated renal disorders exhibited minimum reactivity to streptococcal antigens.

Carotid baroreflexes during hemodialysis.

In 9 regular hemodialysis patients, the carotid baroreceptor reflex was studied using standardized carotid sinus stimulation by neck suction. All patients were studied during predialysis conditions (recirculation), and during dialysis using dialyzate sodium concentrations of 145 and 133 mmoles/l. Baroreceptor stimulation was performed during the recirculation period and after 120-266 minutes of combined dialysis and ultrafiltration. Dialysis alone with either sodium concentration tended to decrease blood pressure. Heart rate as well as plasma renin activity increased significantly during dialysis with either procedure. In contrast to the findings in healthy subjects, heart rate was not influenced by neck suction, possibly reflecting a vagal neuropathy in uremic patients. However, carotid sinus stimulation decreased systolic pressure during recirculation to the same extent as has been found in healthy subjects. Furthermore, the blood pressure response to neck suction was enhanced during dialysis. These findings suggest that the blood pressure decrease during dialysis can not be explained by defective blood pressure control by the carotid sinus baroreceptors.

The influence of dialysis fluid composition on the blood pressure response during dialysis.

To elucidate the relative role of osmolar (sodium) and acetate shifts during dialysis, 6 patients with problems of overhydration underwent rapid ultrafiltration for 1 hr (mean weight reduction 2.0 kg), using the 1 m2 RP 6 dialyzer. Ultrafiltration was carried out at the beginning of each of 5 dialysis treatments at weekly intervals. Ultrafiltration was undertaken without dialysis (controls) and with simultaneous dialysis using acetate (40 mmoles/1) or bicarbonate (25 mmoles/1) in the dialysis fluid with dialyzate sodium concentration of 133 and 145 mmoles/1. The systolic blood pressure and mean arterial pressure which were stable with ultrafiltration only fell slightly when a high dialyzate sodium concentration was used and much further when the dialyzate sodium concentration was kept low. These changes were apparently related to the changes in plasma osmolality. Acetate had no effect on blood pressure at the higher sodium concentration, but a slight (insignificant) additive effect when used in the low-sodium dialyzate. Shifts in osmolality (sodium concentration) seem to be more important than the effect of acetate in inducing dialysis-associated hypotension.

Fulminating anti-A autoimmune hemolysis with anuria in a renal transplant recipient: a therapeutic role of plasma exchange.

In this communication we present a case of fulminating anti-A autoimmune hemolysis with anuria occurring during the postoperative course after a successful renal transplantation. The patient was treated with repeated plasma exchange in an effort to remove antibodies directed against the red cells and also to eliminate the products of hemolysis known to cause acute renal failure. Subsequently the hemolysis receded and the patient regained graft function. Repeated plasma exchange, in addition to immunosuppression, appeared to have contributed to the ultimate recovery of the patient.

Backdiffusion or bicarbonate may stimulate complement activation during haemodialysis with low-flux membranes.

Backdiffusion of dialysate during haemodialysis with low-flux membranes and the use of bicarbonate dialysatebase, may increase the risk for contamination. The influence on the complement system was studied by altering the flux of acetate or bicarbonate dialysate base across the membrane. Eight patients were dialysed with a transmembrane pressure of 100 mm Hg (group I) during the first 60 min to standardize the ultrafiltration (UF) and acetate as dialysate. In eight other patients (group II) the UF was "set at zero" ml during the first 60 min using an FCM 10-1 monitor (Gambro) and bicarbonate as base. The groups were dialysed three times on two hollow-fiber membranes made of Hemophan and cellulose acetate (CA). Blood samples were taken at 0, 15, 60 and 180 min, and analysed for plasma protein, haematocrit and complement C3d. In group II there was a reduction in plasma protein concentration at 15 and 60 min (p < 0.002) for Hemophan and at 60 min (p < 0.01) using CA. C3d was increased at 15 min for both filters (p < 0.03). The reduction of protein in group II was followed by changes in the haematocrit, indicating a backdiffusion of dialysate, which may contribute to the concomittant increase in C3d.

Granulocyte elastase, beta-thromboglobulin, and C3d during acetate or bicarbonate hemodialysis with Hemophan compared to a cellulose acetate membrane.

Twenty-two patients were dialysed in a cross-over design using Hemophan or cellulose acetate membranes. The dialysate buffer was acetate (n = 12) or bicarbonate (n = 10). Blood was sampled at 0, 15, 60 and 180 min and mean values were adjusted for changes in total protein in each sample. At 15 min during dialysis a decrease in leukocytes and platelets occurred with both membranes, irrespective of the buffer (Wilcoxon, p less than 0.006). During dialysis, increases were found in granulocyte elastase inhibitor complex (E- alpha 1-PI), beta-thromboglobulin and C3d. beta 2-microglobulin was not significantly changed in blood after dialysis with Hemophan or cellulose acetate membranes with bicarbonate buffer. Side effects were more pronounced at 180 min during dialysis with bicarbonate in patients using cellulose acetate than with Hemophan (p = 0.021, n = 8). Hemophan seemed to be more favourable than cellulose acetate membranes in regard to leukopenia and E- alpha 1-PI. The dialysate buffer may also alter membrane biocompatibility.