Isolation and partial characterization of cuticular collagen from the parasitic nematodeGaigeria pachyscelis

Summary The cuticle from adultGaigeria pachyscelis was isolated by solubilizing the internal tissues with sodium dodecyl sulphate (SDS) at 37°C. Cuticular protein was extracted with guanidine-HCl and -mercaptoethanol and purified by ammonium sulphate fractionation and DEAE-cellulose chromatography. SDS-polyacrylamide gel electrophoresis of purified protein revealed 2 polypeptides with apparent mol. wts of 58,000 and 74,000. As judged from their hydroxyproline content both of them are collagenous in nature. Results of gel filtration indicate that cuticular collagen exists in two forms, a non-associated form at low concentration and an associated form at high concentration.Acknowledgments. We thank Drs L.N. Singh and H.C. Tewari for providing the necessary facilities. Laboratory assistance of Mr Ram Kishore is highly appreciated.     

Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.     

An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system

The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).     

Children's family change: reports and records of mothers, fathers and children compared

Family change, when adults depart or arrive around children, raises policy issues. Its measurement depends upon the evidence collected and from whom. This paper compares British children's histories obtained from fathers and mothers. The evidence, on one birth cohort of parents, comes from two sources: the National Child Development Study and the ONS Longitudinal Study. The resulting account of family change is not substantially different between parents. There is some under-reporting of children not living with their fathers. This is due to under-reporting by those included in the studies and to under-representation in them of absent fathers and lone parents.     

Germline gain-of-function mutations in SOS1 cause Noonan syndrome

Noonan syndrome, the most common single-gene cause of congenital heart disease, is characterized by short stature, characteristic facies, learning problems and leukemia predisposition. Gain-of-function mutations in PTPN11, encoding the tyrosine phosphatase SHP2, cause approximately 50% of Noonan syndrome cases. SHP2 is required for RAS-ERK MAP kinase (MAPK) cascade activation, and Noonan syndrome mutants enhance ERK activation ex vivo and in mice. KRAS mutations account for <5% of cases of Noonan syndrome, but the gene(s) responsible for the remainder are unknown. We identified missense mutations in SOS1, which encodes an essential RAS guanine nucleotide-exchange factor (RAS-GEF), in approximately 20% of cases of Noonan syndrome without PTPN11 mutation. The prevalence of specific cardiac defects differs in SOS1 mutation-associated Noonan syndrome. Noonan syndrome-associated SOS1 mutations are hypermorphs encoding products that enhance RAS and ERK activation. Our results identify SOS1 mutants as a major cause of Noonan syndrome, representing the first example of activating GEF mutations associated with human disease and providing new insights into RAS-GEF regulation.