M. De Almeida

Isolation and characterisation of two sperm membrane proteins recognised by sperm-associated antibodies in infertile men

Antisperm antibodies eluted from the surface of spermatozoa obtained from infertile men recognised several common epitopes. We tested whether these epitopes were relevant to fertility by isolating the immunodominant 37/36 and 19/18 protein zones. These protein zones were cut out of preparative slab gels and electro‐eluted. The isolated proteins, P36 and P18, were used for biochemical characterisation and to produce specific antibodies in rabbits. The specific reactivity of P36 and P18 with WGA and AAL lectins, respectively, indicated the presence of lactosaminyl structures with sialic acid termini in P36 and of fucosylated residues in P18. Isoelectric focusing showed that the two proteins consist of several polypeptides. Some of these polypeptides were recognised by both human and rabbit antibodies: the pl of these epitopes was around 5.5 for P36 and 8.3–10.3 for P18. Rabbit antibodies detected the corresponding proteins on the sperm heads of methanol‐fixed and of live acrosome‐reacted spermatozoa. Anti‐P36 antibodies bound mainly to the equatorial segment. They reduced the binding and, consequently, the penetration of zona‐free hamster oocytes by human spermatozoa. Anti‐P18 antibodies gave more diffuse staining of the acrosomal and post‐acrosomal regions and reduced sperm–oocyte penetration without a significant effect on sperm binding. These results suggest that P36 and P18 antigens located in different compartments of the sperm head may participate in the sperm–oolemma interaction. We are currently investigating the physiological role of these antigens by sequencing the proteins isolated from the gels. Mol. Reprod. Dev. 57:393–405, 2000.

Skull form and differential mortality by tuberculosis

Abstract The study of patients deceased of pulmonary tuberculosis as compared to all the other ones, shows that men (and not women) have a longer head and face, a narrower face; they probably had a greater stature. The patients deceased of plague and smallpox show the same characteristics. As they were younger, and unmarried for a higher percentage, they took a smaller part in the building of the next generation. Therefore this is a case of selection through differential mortality. The smaller viability of dolichocephals during the great epidemics and endemics explains secular brachycephalisation; the present stopping of this selective pressure makes itself clear through debrachycephalisation and a higher stature concomitant with a more developed hygiene and a lesser mortality through tuberculosis. It is probable that other factors play a part, some of them in a direction contrary to the one brought to light here.