Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene.

Hydroxyl radical (.OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols (SOA). It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride>sodium silicate and ammonium nitrate>ammonium sulfate.

[Increased plasma membrane permeability for Ca2+ in radiation-induced thymocyte apoptosis]. / Uvelichenie pronitsaemosti plazmaticheskoi membrany dlia Ca2+ pri radiatsionno-indutsirovannom apoptoze timotsitov.

Parameters of the Ca2+ permeability (the 45Ca influx rate in the presence of orthovanadate blocking the Ca(2+)-ATPhase, and the initial rate of the 45Ca uptake) and the DNA fragmentation were determined in rat thymocytes after gamma-irradiation-induced (with a dose of 5 Gy) apoptosis. Within the first 30-90 min after irradiation, the 45Ca influx rate that is characteristic of the membrane passive permeability remained unchanged. The initial rate of the 45Ca uptake that is characteristic of the Ca2+ exchange almost doubled. In 90-180 min, the rate of the 45Ca influx in the irradiated cells increased 1.5 to 2.0 times. An increase in the DNA fragmentation was observed in 90-120 min after irradiation of thymocytes; in 3 h, it developed up to 50%. Thus, modification of the membrane Ca2+ permeability in the irradiated thymocytes precedes a stage of initiation of the DNA degradation. A degree of disturbance of the membrane passive permeability increases as the thymocyte apoptosis progresses. The obtained data suggest that disturbance of the passive Ca2+ permeability and the intracellular Ca2+ homeostasis are responsible for the apoptosis of lethally irradiated thymocytes.