Sexual selection for genetic compatibility: the role of the major histocompatibility complex on cryptic female choice in Chinook salmon (Oncorhynchus tshawytscha).

Cryptic female choice (CFC), a form of sexual selection during or post mating, describes processes of differential sperm utilization by females to bias fertilization outcomes towards certain males. In Chinook salmon (Oncorhynchus tshawytscha) the ovarian fluid surrounding the ova of a given female differently enhances the sperm velocity of males. Sperm velocity is a key ejaculate trait that determines fertilization success in externally fertilizing fishes, thus the differential effect on sperm velocity might bias male fertilization outcomes and represent a mechanism of CFC. Once sperm reach the oocyte, CFC could potentially be further facilitated by sperm-egg interactions, which are well understood in externally fertilizing marine invertebrates. Here, we explored the potential genetic basis of both possible mechanisms of CFC by examining whether the genotypic combinations of mates (amino-acid divergence, number of shared alleles) at the major histocompatibility complex (MHC) class I and II explain the variation in sperm velocity and/or male fertilization success that is not explained by sperm velocity, which might indicate MHC-based sperm-egg interactions. We recorded sperm velocity in ovarian fluid, employed paired-male fertilization trials and evaluated the fertilization success of each male using microsatellite-based paternity assignment. We showed that relative sperm velocity was positively correlated with fertilization success, confirming that the differential effect on sperm velocity may be a mechanism of CFC in Chinook salmon. The variation in sperm velocity was independent of MHC class I and II. However, the MHC class II divergence of mates explained fertilization success, indicating that this locus might influence sperm-egg interactions.

Extensive variation at MHC DRB in the New Zealand sea lion (Phocarctos hookeri) provides evidence for balancing selection.

Marine mammals are often reported to possess reduced variation of major histocompatibility complex (MHC) genes compared with their terrestrial counterparts. We evaluated diversity at two MHC class II B genes, DQB and DRB, in the New Zealand sea lion (Phocarctos hookeri, NZSL) a species that has suffered high mortality owing to bacterial epizootics, using Sanger sequencing and haplotype reconstruction, together with next-generation sequencing. Despite this species' prolonged history of small population size and highly restricted distribution, we demonstrate extensive diversity at MHC DRB with 26 alleles, whereas MHC DQB is dimorphic. We identify four DRB codons, predicted to be involved in antigen binding, that are evolving under adaptive evolution. Our data suggest diversity at DRB may be maintained by balancing selection, consistent with the role of this locus as an antigen-binding region and the species' recent history of mass mortality during a series of bacterial epizootics. Phylogenetic analyses of DQB and DRB sequences from pinnipeds and other carnivores revealed significant allelic diversity, but little phylogenetic depth or structure among pinniped alleles; thus, we could neither confirm nor refute the possibility of trans-species polymorphism in this group. The phylogenetic pattern observed however, suggests some significant evolutionary constraint on these loci in the recent past, with the pattern consistent with that expected following an epizootic event. These data may help further elucidate some of the genetic factors underlying the unusually high susceptibility to bacterial infection of the threatened NZSL, and help us to better understand the extent and pattern of MHC diversity in pinnipeds.

Comparison of the phenylenediamine isomers bioactivation by the green alga Chlamydomonas reinhardtii.

The correlation between the chemical structure of arylamines meta-, orto-, para-phenylenediamine (m-PDA, o-PDA, p-PDA), and their mutagenic activity is known. It is accepted that these promutagenic compounds are metabolized to ultimate mutagens in mammals and higher plants. In our previous work, we used the alga Chlamydomonas reinhardtii as the activating organism and the bacteria Salmonella typhimurium and yeast Saccharomyces cerevisiae as the genetic indicators for m-PDA activation. In the present work, we used the same activation system for o-PDA and p-PDA activation. Different responses of the yeast and algal wild-type strain and of the repair-deficient strains to the toxic and mutagenic effects of o-PDA and p -PDA were observed. p-PDA had the most toxic effect on both intact yeast and algal cells and in the algal cell/microbe coincubation assays. Concerning repair-deficient algal strains, the recombination-deficient strain was the most sensitive to both compounds tested, indicating that the recombination process played an important role in the DNA repair of arylamines. The rank order of the PDA isomers mutagenicity (including m-PDA) was o-PDA > m-PDA > p-PDA for revertants in intact yeast and forward mutants in algae; m-PDA > o-PDA > p-PDA in the algal cell/S. typhimurium long-term coincubation assay, the algal cell/S. cerevisiae coincubation assay, and the intact S. cerevisiae assay for gene convertants as well.

[Auditory screening of neonates using an objective method--otoacoustic emissions]. / Skríningové vysetrenie sluchu u novorodencov objektívnou metódou--otoakustickými emisiami.

Screening for hearing loss in children in Slovak republic with non-objective methods detects only deaf children, mean age of the diagnosis establishment is even 2.5 years. It is necessary for healthy child development to detect and treat a child with bilateral defect before 1 year of age. Preliminary results of auditory screening in 456 newborns with objective method of otoacoustic emissions (OAE) proved the necessity of otoacoustic screening in all risk newborns. In one of 204 risk newborns serious hearing loss was proved with BERA examination and in next 8 of them it is suspected according to the OAE results and additional tympanometric examination with the A curve. Until now in newborn without risk of hearing loss in history were not detected bilateral hearing loss, only unilateral, not requiring treatment. (Fig. 1, Tab. 2. Ref. 9.)