Estimation of the proportion of genetically unbalanced spermatozoa in the semen of boars carrying chromosomal rearrangements using FISH on sperm nuclei

Many chromosomal rearrangements are detected each year in France on young boars candidates for reproduction. The possible use of these animals requires a good knowledge of the potential effect of the rearrangements on the prolificacy of their mates. This effect can be estimated by an accurate determination of the rate of unbalanced spermatozoa in the semen of boars which carry the rearrangements. Indeed, these spermatozoa exhibiting normal fertilizing ability are responsible for an early embryonic mortality, and then, for a decrease of the litter sizes. The "spermFISH" technique, i.e. fluorescent in situ hybridization on decondensed sperm heads, has been used on several occasions in Man, in this perspective. In livestock species, this method was formerly used mainly for semen sexing purposes. We used it, for the first time, to estimate the rates of imbalance in the semen of four boars carrying chromosomal rearrangements: two reciprocal translocations, rcp(3;15)(q27;q13) and rcp(12;14)(q13;q21), as well as two independent cases of trisomy 18 mosaicism. The rates of unbalanced gametes were relatively high for the two reciprocal translocations (47.83% and 24.33%, respectively). These values differed from the apparent effects of the rearrangements estimated using a limited number of litters: a decrease in prolificacy of 23% (estimation obtained using the results of 6 litters) and 39% (57 litters), respectively for the 3/15 and 12/14 translocations. The imbalance rates were much lower for the trisomy mosaics (0.58% and 1.13%), suggesting a very moderate effect of this special kind of chromosomal rearrangement.     

Bovine sperm capacitation: assessment of phosphodiesterase activity and intracellular alkalinization on capacitation-associated protein tyrosine phosphorylation

Mammalian sperm capacitation is the obligatory maturational process leading to the development of the fertilization-competent state. Heparin is known to be a unique species-specific inducer of bovine sperm capacitation in vitro and glucose a unique inhibitor of this induction. Heparin-induced capacitation of bovine sperm has been shown to correlate with protein kinase A (PKA)-dependent protein tyrosine phosphorylation driven by an increase in intracellular cAMP. This study examines the possible roles of cyclic nucleotide phosphodiesterase (PDE) activity and intracellular alkalinization on bovine sperm capacitation and the protein tyrosine phosphorylation associated with it. Measurement of whole cell PDE kinetics during capacitation reveals neither a substantial change with heparin nor one with glucose: PDE activity is effectively constitutive in maintaining intracellular cAMP levels during capacitation. In contrast to a transient increase in intracellular pH, a sustained increase in medium pH by switching from 5% CO(2)/95% air incubation to 1% CO(2)/99% air incubation over 4 hr in the absence of heparin resulted in an increase in protein tyrosine phosphorylation and in the extent of induced acrosome reaction comparable to that observed following heparin-induced capacitation in 5% CO(2). These results suggest that increased bicarbonate-dependent adenylyl cyclase activity, driven by alkalinization, increases intracellular cAMP and so increases PKA activity mediating protein tyrosine phosphorylation. Quantitative analysis of the lactic acid production rate by bovine sperm glycolysis accounts fully for intracellular acidification sufficient to offset heparin-induced alkalinization, thus inhibiting capacitation. The mechanism by which heparin uniquely induces intracellular alkalinization in bovine sperm leading to capacitation remains obscure, inviting future investigation.     

The nucleotide sugar transporters AtUTr1 and AtUTr3 are required for the incorporation of UDP‐glucose into the endoplasmic reticulum,are essential for pollen development and are needed for embryo sac progress in Arabidopsis thaliana

Uridine 5′‐diphosphate (UDP)‐glucose is transported into the lumen of the endoplasmic reticulum (ER), and the Arabidopsis nucleotide sugar transporter AtUTr1 has been proposed to play a role in this process; however, different lines of evidence suggest that another transporter(s) may also be involved. Here we show that AtUTr3 is involved in the transport of UDP‐glucose and is located at the ER but also at the Golgi. Insertional mutants in AtUTr3 showed no obvious phenotype. Biochemical analysis in both AtUTr1 and AtUTr3 mutants indicates that uptake of UDP‐glucose into the ER is mostly driven by these two transporters. Interestingly, the expression of AtUTr3 is induced by stimuli that trigger the unfolded protein response (UPR), a phenomenon also observed for AtUTr1, suggesting that both AtUTr1 and AtUTr3 are involved in supplying UDP‐glucose into the ER lumen when misfolded proteins are accumulated. Disruption of both AtUTr1 and AtUTr3 causes lethality. Genetic analysis showed that the atutr1 atutr3 combination was not transmitted by pollen and was poorly transmitted by the ovules. Cell biology analysis indicates that knocking out both genes leads to abnormalities in both male and female germ line development. These results show that the nucleotide sugar transporters AtUTr1 and AtUTr3 are required for the incorporation of UDP‐glucose into the ER, are essential for pollen development and are needed for embryo sac progress in Arabidopsis thaliana.     

CHANGE OF UBIQUITINATED PROTEINS DURING THE CELL CYCLE IN CHLAMYDOMONAS (CHLOROPHYTA)1

Changes in the amount of heat shock-related ubiquitinated proteins in Chlamydomonas were investigated during the cell cycle and gamete induction. In a division-synchronized culture induced by periodic illumination, the amount of the 28-kDa ubiquitinated protein increased during the dark phase. This increase correlated with the increase of total DNA. Such an increase was repressed when nuclear DNA replication was inhibited with aphidicolin. These results suggest that ubiquitination to form the 28-kDa protein is involved in nuclear DNA replication or during the cell cycle. The amount of 31-kDa ubiquitinated protein gradually increased throughout the light phase and decreased in the dark phase. The amount of 28-kDa ubiquitinated protein also increased during gamete induction caused by nitrogen starvation, while that of the 31-kDa did not. These results suggest that the change of ubiquitination of 28-kDa protein mat play a fundamental role in the cell cycle and gamete induction in Chlamydomonas.     

POSTMENOPAUSAL MOTHERHOOD: IMMORAL,ILLEGAL? A CASE STUDY

The paper explores the ethics of post-menopausal motherhood by looking at the case of Adriana Iliescu, the oldest woman ever to have given birth (so far). To this end, I will approach the three most common objections brought against the mother and/or against the team of healthcare professionals who made it happen: the age of the mother, the fact that she is single, the appropriateness of her motivation and of that of the medical team.     

Sex allocation in haplodiploids is mediated by egg size: evidence in the spider mite Tetranychus urticae Koch

Haplodiploid species display extraordinary sex ratios. However, a differential investment in male and female offspring might also be achieved by a differential provisioning of eggs, as observed in birds and lizards. We investigated this hypothesis in the haplodiploid spider mite Tetranychus urticae, which displays highly female-biased sex ratios. We show that egg size significantly determines not only larval size, juvenile survival and adult size, but also fertilization probability, as in marine invertebrates with external fertilization, so that female (fertilized) eggs are significantly larger than male (unfertilized) eggs. Moreover, females with on average larger eggs before fertilization produce a more female-biased sex ratio afterwards. Egg size thus mediates sex-specific egg provisioning, sex and offspring sex ratio. Finally, sex-specific egg provisioning has another major consequence: male eggs produced by mated mothers are smaller than male eggs produced by virgins, and this size difference persists in adults. Virgin females might thus have a (male) fitness advantage over mated females.     

GROWTH AND PROBABLE GAMETE FORMATION IN THE MARINE DINOFLAGELLATE CERATIUM SCHRANKII1

Growth and formation of probable gametes in clonal cultures of Ceratium schrankii Kofoid isolated from the Gulf of Naples were monitored at 15, 20 and 25°C (12:12h LD period). Sustained division rates (k) of 0.15 div d ^?1 at 15°C and elevated ones at 20°C (0.27 div d^?1) and 25°C (0.25 div d^?1) were obtained. “Gamete” formation occurred at each temperature with few “gametes” observed at 15°C, and the greatest numbers at 20° and 25°C. This process in each parent cell involved two successive divisions with the first division forming tow “pregametes” which, within a few hours, divided again to form four motile unicells. These “gametes” remained motile for at least 24 h and normally survived for no longer tahn 48 h. Depending on the initial population at the onset of “gamete” formation, the impact on Ceratium populations was to cause either a momentary pause in log growth or a reversible decline in the populaiton.     

Regulation of gamete release in the economic brown seaweed <Emphasis Type="Italic">Hizikia fusiforme</Emphasis> (Phaeophyta)

Gamete release is an essential event in artificial seeding of the economic brown seaweed, Hizikia fusiforme. Mass egg release occurred in the dark, with few eggs being discharged in the light. Release of eggs was elicited with eight practical salinity units (one PSU ≡ 1 g sea salts l⁻¹) and was inhibited by salinity levels >32 PSU. Egg release was optimal at 23 °C, and was decreased by 72% in agitated seawater compared to unstirred seawater. Inhibitors of photosynthesis and ions channels suppressed egg release, indicating that this process was physiologically associated with photosynthetic activity and ion transport.     

Experimental sexual selection in Chlamydomonas

Sexual and asexual lines of the unicellular chlorophyte Chlamydomonas reinhardtii were propagated for about 100 sexual cycles and 1000 vegetative cycles in contrasted environments, liquid and solid growth media, in order to generate divergent natural and sexual selection. Sexual lines were transferred by many zygotes or by a single zygote in each sexual generation. By the end of the experiment zygote production was in the order sexual mass-transfer>sexual single-zygote>asexual>ancestor. The direct response to sexual selection was large, with zygote production increasing by about two orders of magnitude, mainly because mating had become spontaneous instead of being invoked by nitrogen starvation. Asexual lines became sexually sterilized by the fixation of a single mating type. Sexual selection caused a radical shift in the gender system, with homothallism spreading to high frequency in all sexual lines of this normally heterothallic species. This may have been caused by the transposition of a mating-type gene to an autosome. No substantial degree of environment-specific mating evolved, however, and thus no sexual isolation indicative of incipient speciation. It is possible that selection experiments of this kind are unlikely to induce sexual isolation because mating-type genes evolve in a saltatory fashion.