Two recent studies with white males have shown that genotypes associated with high levels of monamine oxidase A (MAOA) protect against the impact of childhood maltreatment and adversity on the development of antisocial behavior and conduct disorder.
Males have shown antagonistic behaviors such as attacks, pursuits, threats, assertion, fighting, and subordination.
This finding is interesting since longevity studies in females and males have shown that females have less oxidative stress than males [47], [48].
However, responsiveness in extra-pair trials was neither related to the song rate of these males during extra-pair trials (experiment 3; male averages; r = −0.01, N = 85, P = 0.91; Fig. 3b) nor to the song rate these males had shown before pair formation (experiment 1; r = −0.05, N = 84, P = 0.63).
On the other hand, expression studies in males have shown that MECP2 mRNA levels do not correlate with disease severity [19].
The studies carried out in Europe on C. trachomatis infection among young males have shown high rates ranging from 7.8 13.3%[ 1, 6- 11].
Experimental studies in males have shown that testosterone administration reduces lipid uptake by intraabdominal fat (Mårin et al. 1996) and also reduces visceral fat and improves insulin sensitivity (Mårin 1995; Mårin et al. 1992 , 1993.
Among species of the Drosophila simulans clade, double mating of females to conspecific and heterospecific males have shown that the majority of progeny is fathered by the conspecific male regardless of the mating order, with the breakdown in competitive success of the heterospecific males being attributed to poor sperm displacement ability (Price et al. 2000, 2001).
Cytological analyses of sterile hybrid males have shown a variety of subtle sperm development changes, such as abnormal sperm individualization timing, excessive cellular debris between sperm bundles or sperm tails with disrupted axoneme to mitochondrial derivatives relationships that can result from anomalies during late stages of sperm development [ 16, 27, 28].
