Variability within the Seychelles Cytoplasmic Incompatibility System in Drosophila Simulans

In Drosophila simulans, we described a cytoplasmic incompatibility (CI) system (Seychelles) restricted to insular populations that harbor the mitochondrial type SiI. Since then, these populations have been shown to be heterogeneous, some being infected by one Wolbachia genetic variant only (wHa), while others are infected simultaneously by wHa and by another variant (wNo) always found in association with wHa. We have experimentally obtained two D. simulans strains only infected by the wNo variant. This variant determines its own cytoplasmic incompatibility type. In particular, the cross between wNo-bearing flies and wHa-bearing ones is bidirectionally incompatible. The Seychelles CI type, stricto sensu, is distinguished by being determined by the simultaneous presence of two Wolbachia variants that we found to be mutually incompatible. In addition, we observed incomplete maternal transmission of the Wolbachia.     

Antibody penetration into living cells. II. Anti-ribonucleoprotein IgG penetrates into Tgamma lymphocytes causing their deletion and the abrogation of suppressor function.

We have previously shown that an anti-ribonucleoprotein (RNP) IgG can penetrate into live human mononuclear cells (MNC) having receptors for the Fc portion of IgG. Because T cells with such receptors (Tgamma cells) seem to behave as suppressor cells in immune regulation and because this suppressor function is diminished in diseases where antinuclear antibodies appear, we considered the possibility that antinuclear IgG antibody could penetrate Tgamma cells and affect them. Herein we show that fluorescein-labeled anti-RNP IgG can penetrate into Tgamma cells, enriched by either mitogenic stimulation or separation with a subpopulation of T cells with low affinity for sheep erythrocytes. Incubation of MNC with anti-RNP IgG before carrying out the separation procedures resulted in apparent loss of Tgamma cells at the end of separation. To confirm that deletion had actually occurred, we performed a cytotoxicity assay using 51Cr-labeled T cells. Anti-RNP IgG had a significantly higher cytotoxic effect that normal IgG on T cells, particularly on those with low affinity for sheep erythrocytes that include most Tgamma cells. Suppressor cell function studied in a system where it was expanded, by either 7-day culture or incubation with concanavalin A, and detected in a reverse plaque-forming cell assay with rabbit anti-human immunoglobulin-developing antibody was found to be abrogated by the addition of anti-RNP IgG to the suppressor function-expanding cultures. Controls in Ig-free medium, or medium supplemented with normal human IgG, aggregated normal human IgG, BSA-anti-BSA immune complexes, or F(ab')2 fragments of the anti-RNP IgG, did not abrogate suppressor cell function. This indicates that the abrogation of suppressor cell function by anti-RNP IgG is due to its penetration into Tgamma cells. Suppressor cell loss and/or dysfunction caused by penetration of antinuclear antibodies into Tgamma cells may lead to the self-perpetuation of autoimmune disease.     

Experimental dissection of flagellar surface motility in chlamydomonas

Experiments have explored the possible relationships between the flagellar surface motility of chlamydomonas, visualized as translocation of polystyrene beads by paralyzed (pf) mutants (Bloodgood, 1977, J. Cell Biol. 15:983-989), and the capacity of gametic flagella to participate in the mating reaction. While vegetative and gametic flagella bind beads with equal efficiencies and are capable of transporting them along entire flagellar lengths, beads on vegetative flagella are primarily associated with the proximal half of the flagella whereas those of gametic flagella exhibit no such preference. This difference may relate to the "tipping" response of gametes during sexual flagellar agglutination (Goodenough and Jurivich, 1978, J. Cell Biol. 79:680-693). Colchicine, vinblastine, chymotrypsin, cytochalasins B and D, and anti-β-tubulin antiserum are all able to inhibit the binding of beads to the flagellar suface. Trysin digestion and an antiserum directed against whole chlamydomonas flagella have no effect on the ability of flagella to bind beads, but the beads remain immobile. These results suggest that at least two flagellar activities participate in surface motility: (a) bead binding, which may involve a tubulin-like component at the flagellar surface; and (b) bead translocation, which may depend on a second component (e.g. an ATPase) of the flagellar surface. Surface motility is shown to be distinct from gametic adhesiveness per se, but it may participate in concentrating dispersed agglutinins, in driving them toward the flagellar tips, and/or in generating a signal-to-fuse from the flagellar tips to the cell body. Directly supporting these concepts is the observation that bound beads remain immobilized at the flagellar tips during the "tip-locking" stage of pf x pf matings, and the observation that bound ligands such as antibody fail to be tipped by trypsinized flagella.     

Efficiency of essential oil (Satureja montana) in controlling the ascospherosis in the honey bee (Apis mellifera) under field conditions.

With the aim of testing its effect in the control of ascosphaerosis in bees, the essential oil of ajedra was incorporated into three types of feed in five different concentrations. Syrup (water and honey) with 0.1% were the best tolerated by the bees, with no colonial changes after a single feed. Later, the ascosphaerosis was introduced in a controlled manner into eight hives. For this, a 10 e6/ml spore suspension was applied by nedulisor three times a week for four weeks to ensure its abundant presence inside the hives. This was continued for the next four weeks period, and at the same time portions of brood-comb in a known state (24 h before operculation) were removed from the hives and heat shocked for 24 h (22 -/+ 2 degrees C), then replaced in the hives for their opercultion, finally removing them and maintaining them at 35 degrees C and 70% relative humidity until the appearance of typical disease symptoms (mummification of the larvae).The hives were randomly divided into two groups of four. One group received 500 ml of syrup with 0.1% oil of ajedra, twice a week for four weeks. The other was kept as the control, receiving syrup without medication. 27.6% of the selected larvae in the treated hives showed mummification, compared with 79.1% in the control hives. The treatment was perfectly tolerated by the bee colonies, showing no changes in their subsequent development.