An extinct vertebrate preserved by its living hybridogenetic descendant.

Hybridogenesis is a special mode of hybrid reproduction where one parental genome is eliminated and the other is transmitted clonally. We propose that this mechanism can perpetuate the genome of extinct species, based on new genetic data from Pelophylax water frogs. We characterized the genetic makeup of Italian hybridogenetic hybrids (P. kl. hispanicus and esculentus) and identified a new endemic lineage of Eastern-Mediterranean origin as one parental ancestor of P. kl. hispanicus. This taxon is nowadays extinct in the wild but its germline subsists through its hybridogenetic descendant, which can thus be considered as a "semi living fossil". Such rare situation calls for realistic efforts of de-extinction through selective breeding without genetic engineering, and fuels the topical controversy of reviving long extinct species. "Ghost" species hidden by taxa of hybrid origin may be more frequent than suspected in vertebrate groups that experienced a strong history of hybridization and semi-sexual reproduction

Characterisation and neutralisation of Aeromonas hydrophila enterotoxin in the rabbit ileal-loop model

Cell-free culture filtrates and crude enterotoxin preparations from six strains of Aeromonas hydrophiza caused the accumulation of fluid in rabbit ileal loops. This activity was due to a non-dialysable, heat and acid-labile antigenic protein and was lost when culture filtrates and crude enterotoxin preparations were heated at 60°C for 20 min. or 56°C for 30 min. respectively. Maximum activity was observed at pH 8.0-10.0; there was a gradual loss at lower pH and activity was abolished in culture filtrates held at pH 3.0 and crude enterotoxin preparations held at pH 4.0. Titration of the crude enterotoxin preparations in rabbit ileal loops showed that the ED50 (equivalent to 1 unit of toxin) was contained in 25 μg of protein; a logarithmic plot of the neutralisation coefficients against antiserum concentrations showed that one unit of antitoxin was contained in 42×10−4 ml of the antiserum

Potentiometric Studies on the Complex Formation of Some Ln(III) Ions with 4-Nitrocatechol

756-75

Potentiometric Studies on the Complex Formation of Some Ln(III) Ions with 4-Nitrocatechol

756-75

Current-induced two-level fluctuations in pseudo spin-valves (Co/Cu/Co) nanostructures

Two-level fluctuations of the magnetization state of pseudo spin-valve pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires (~40 nm in diameter, 6000 nm in length) are triggered by spin-polarized currents of 10^7 A/cm^2 at room temperature. The statistical properties of the residence times in the parallel and antiparallel magnetization states reveal two effects with qualitatively different dependences on current intensity. The current appears to have the effect of a field determined as the bias field required to equalize these times. The bias field changes sign when the current polarity is reversed. At this field, the effect of a current density of 10^7 A/cm^2 is to lower the mean time for switching down to the microsecond range. This effect is independent of the sign of the current and is interpreted in terms of an effective temperature for the magnetization.Comment: 4 pages, 5 figures, revised version, to be published in Phys. Rev. Let

The effect of phylogeographic history on species boundaries: a comparative framework in Hyla tree frogs.

Because it is indicative of reproductive isolation, the amount of genetic introgression across secondary contact zones is increasingly considered in species delimitation. However, patterns of admixture at range margins can be skewed by the regional dynamics of hybrid zones. In this context, we posit an important role for phylogeographic history: hybrid zones located within glacial refugia (putatively formed during the Late-Pleistocene) should be better defined than those located in post-glacial or introduced ranges (putatively formed during the Holocene and the Anthropocene). We test this hypothesis in a speciation continuum of tree frogs from the Western Palearctic (Hyla), featuring ten identified contacts between species spanning Plio-Pleistocene to Miocene divergences. We review the rich phylogeographic literature of this group and examine the overlooked transition between H. arborea and H. molleri in Western France using a multilocus dataset. Our comparative analysis supports a trend that contacts zones resulting from post-glacial expansions and human translocations feature more extensive introgression than those established within refugial areas. Integrating the biogeographic history of incipient species, i.e. their age since first contact together with their genetic divergence, thus appears timely to draw sound evolutionary and taxonomic inferences from patterns of introgression across hybrid zones

The changing trend of alloimmunization in antenatal females: experience from a tertiary care centre in north-western India

Background: Haemolytic disease of the foetus and new-born (HDFN) is a major concern during the antenatal period, especially in countries with low human development index (HDI). The guidelines for antenatal screening and management significantly vary from one geographical region to another. Since the introduction of RhIG immunoprophylaxis, the incidence of HDFN caused by alloimmunization to D antigen has markedly reduced, while that caused by other minor blood group antigens has not been addressed significantly and needs to be given due consideration.Methods: The study was carried out to evaluate the incidence of alloimmunization and analyse various factors associated with HDFN in north-western India. A total of 1700 antenatal cases were evaluated over a period of 20 months, antibody screening and identification was performed on their samples and results were analysed.Results: Out of the 1700 cases, 21 were detected to have the presence of an alloantibody with a prevalence of 1.24%. Out of these, 11 were Rh (D) negative while the remaining 10 were Rh (D) positive. The rate for alloimmunization was higher in females who had a history of blood transfusion (1.24%), bad obstetric history (1.24%), and multigravida status (1.24%).Conclusions: Screening all pregnant females for alloimmunization to RBC antigens, irrespective of their Rh status will help in minimizing the incidence of the HDFN. The practice of providing partial phenotype matched blood to the females of the childbearing age group should be encouraged to reduce the overall incidence of alloimmunization and HDFN