Repolitisations féministes et queer du cerveau

L’histoire des relations entre biologie et politique féministe est tendue et contradictoire. Cela paraît d’autant plus flagrant aujourd’hui à l’âge d’or des neurosciences qui ramènent les arguments de supériorité masculine, le caractère inéluctable des différences de genre et la prédominance de l’hétérosexualité à une affaire de cerveau. Dans cet article, nous analysons les points d’intersection propres aux sciences du cerveau et du féminisme. Ces deux champs de recherche entretiennent selon nous des rapports conflictuels mais parfois aussi productifs, y compris dans leurs rapports à l’activisme politique. Ces rapports peuvent être caractérisés en référence à trois directions de recherche principales : des « déstabilisations », des « reconstructions » et des « recontextualisations ». En guise de conclusion, nous terminons par quelques réflexions sur les conditions sociologiques de l’engagement dans une économie politique des neurosciences.[1] [1]Traduit de l’anglais par Marc Gagnepain. Pour une brève présentation de l’article et du dossier thématique dans lequel il s’inscrit, nous renvoyons le/la lecteur/trice à l’article introductif de Bovet, Kraus, Panese, Pidoux et Stücklin, « Les neurosciences à l’épreuve de la clinique et des sciences sociales. Regards croisés ».

Slow fertilization of stickleback eggs: the result of sexual conflict?

BACKGROUND: The fertilization success in sperm competition in externally fertilizing fish depends on number and quality of sperm. The time delay between sequential ejaculations may further influence the outcome of sperm competition. Such a time interval can load the raffle over fertilization if fertilization takes place very fast. Short fertilization times are generally assumed for externally fertilizing fish such as the three-spined stickleback (Gasterosteus aculeatus). In this pair-spawning fish, territorial males often try to steal fertilizations in nests of neighbouring males. This sneaking behaviour causes sperm competition. Sneakers will only get a share of paternity when eggs are not fertilized immediately after sperm release. Contrary to males, females may be interested in multiple paternity of their clutch of eggs. There thus may be a sexual conflict over the speed of fertilization. RESULTS: In this study we used two different in vitro fertilization experiments to assess how fast eggs are fertilized in sticklebacks. We show that complete fertilization takes more than 5 min which is atypically long for externally fertilizing fishes. CONCLUSION: This result suggests that the time difference does not imply high costs to the second stickleback male to ejaculate. Slow fertilization (and concomitant prolonged longevity of sperm) may be the result of sexual conflict in which females aimed at complete fertilization and/or multiple paternity.

Sexual function after vaginal and abdominal fistula repair

OBJECTIVE The purpose of this study was to compare clinical outcomes and sexual function between transvaginal and transabdominal repairs of vesicovaginal fistulae (VVF). STUDY DESIGN Participants (99 women with VVF at a tertiary referral center) were treated with urinary catheterization for 12 weeks and, if the procedure was unsuccessful, underwent repair either the transvaginal (Latzko) or transabdominal technique. Objective clinical parameters were analyzed; subjective outcomes were recorded prospectively at the 6-month follow-up examination with the use of the female sexual function index to evaluate sexual function and the visual analogue scale to measure general disturbance by the fistula. RESULTS After bladder drainage for 12 weeks, 8 patients had spontaneous fistula closure. Demographic variables were similar in the transvaginal (n = 60) and transabdominal (n = 31) repair groups. The transvaginal procedure showed significantly shorter operation times, less blood loss, and shorter hospital stay. Continence rates 6 months after surgery were 82% (transvaginal) and 90% (transabdominal). Sexual function in the 64 sexually active patients was significantly improved, and overall disturbance by the fistula was reduced with both operative techniques. Neither surgical intervention was superior to the other regarding any domain of sexual function or visual analog scale. CONCLUSION Fistula repair improves sexual function and quality of life with no difference attributable to surgical route. Given this and that operating time, blood loss and length of stay are less with the transvaginal approach, the transvaginal approach is preferred in VVF repair if fistula and patient characteristics are suitable.

Explosive speciation rates and unusual species richness in haplochromine cichlid fishes: Effects of sexual selection

Ancient lakes are often unusually species rich, mostly as a result of radiation and species-flock formation having taken place in only one or a few of many taxa present. Understanding why some taxa radiate and others do not is at the heart of understanding biodiversity. In this chapter I discuss possible explanations for disproportionally large species numbers in some cichlid fish lineages in East African Great Lakes: the halochromine cichlid fishes in Lakes Victoria and Malawi. I show that speciation rates in this group are higher than in any other lacustrine fish radiation. Against this background, I review hypotheses put forward to explain diversity in cichlid species flocks. The evolution of species diversity requires three processes: speciation, ecological radiation and anatomical diversification, and it is wrong to consider hypotheses that are relevant to different processes as alternatives to each other. The African cichlid species flocks show unusually high ecological species packing in several phylogenetic groups and unusually high speciation rates in haplochromines. Therefore, it maybe concluded that at least two evolutionary models are required to explain the difference between cichlid diversity and other fish diversity in East African Lakes: one for speciation in haplochromines and one for coexistence. Subsequently I review work on speciation in haplochromines, and in particular studies aimed at testing the hypothesis of speciation by sexual selection. Haplochromines have a polygynous mating system, conducive to sexual selection, but other polygynous cichlids are not particularly species rich. This suggests that more than just strong sexual selection is required to explain haplochromine species richness. Recent palaeoecological evidence undermines the previously popular hypotheses that explained the species richness of Lake Victoria in terms of speciation under varying natural or sexual selection regimes in satellite lakes or in isolated lake basins. I summarize experimental and comparative studies, which provide evidence for two mechanisms of sympatric speciation by disruptive sexual selection on polymorphic coloration. Such modes of speciation may explain (i) the high speciation rates in colour polymorphic lineages of haplochromine cichlids under conditions where colour variation is visible in clear water, and (ii) in combination with factors that affect population survival, the unusual species richness in haplochromine species flocks. I argue that sexual selection, if disruptive, can accelerate the pace of adaptive radiation because the resultant genetic population fragmentation allows a much increased rate of differential response to disruptive natural selection. Hence, the ecological pattern of diversity resembles that produced by disruptive natural selection, with the difference that disruptive sexual selection continues to cause (gross) speciation even after niche space is saturated. This may explain the unusually high numbers of very closely related and ecologically similar species in haplochromine species flocks. The role of disruptive sexual selection is twofold: it not only causes speciation, but also maintains reproductive isolation in sympatry between species that have evolved in sympatry or allopatry. Therefore, the maintenance of diversity in species flocks that originated through sexual selection depends on the persistence of the selection regime within the environmental signal space under which that diversity evolved.

Antibiotic-Resistant Neisseria gonorrhoeae Spread Faster with More Treatment, Not More Sexual Partners.

The sexually transmitted bacterium Neisseria gonorrhoeae has developed resistance to all antibiotic classes that have been used for treatment and strains resistant to multiple antibiotic classes have evolved. In many countries, there is only one antibiotic remaining for empirical N. gonorrhoeae treatment, and antibiotic management to counteract resistance spread is urgently needed. Understanding dynamics and drivers of resistance spread can provide an improved rationale for antibiotic management. In our study, we first used antibiotic resistance surveillance data to estimate the rates at which antibiotic-resistant N. gonorrhoeae spread in two host populations, heterosexual men (HetM) and men who have sex with men (MSM). We found higher rates of spread for MSM (0.86 to 2.38 y-1, mean doubling time: 6 months) compared to HetM (0.24 to 0.86 y-1, mean doubling time: 16 months). We then developed a dynamic transmission model to reproduce the observed dynamics of N. gonorrhoeae transmission in populations of heterosexual men and women (HMW) and MSM. We parameterized the model using sexual behavior data and calibrated it to N. gonorrhoeae prevalence and incidence data. In the model, antibiotic-resistant N. gonorrhoeae spread with a median rate of 0.88 y-1 in HMW and 3.12 y-1 in MSM. These rates correspond to median doubling times of 9 (HMW) and 3 (MSM) months. Assuming no fitness costs, the model shows the difference in the host population's treatment rate rather than the difference in the number of sexual partners explains the differential spread of resistance. As higher treatment rates result in faster spread of antibiotic resistance, treatment recommendations for N. gonorrhoeae should carefully balance prevention of infection and avoidance of resistance spread.