Superconductivity in the non-oxide perovskite MgCNi3

The interplay of magnetic interactions, the dimensionality of the crystal structure and electronic correlations in producing superconductivity is one of the dominant themes in the study of the electronic properties of complex materials. Although magnetic interactions and two-dimensional structures were long thought to be detrimental to the formation of a superconducting state, they are actually common features of both the high transition-temperature (Tc) copper oxides and low-Tc material Sr2RuO4, where they appear to be essential contributors to the exotic electronic states of these materials. Here we report that the perovskite-structured compound MgCNi3 is superconducting with a critical temperature of 8 K. This material is the three-dimensional analogue of the LnNi2B2C family of superconductors, which have critical temperatures up to 16 K (ref. 2). The itinerant electrons in both families of materials arise from the partial filling of the nickel d-states, which generally leads to ferromagnetism as is the case in metallic Ni. The high relative proportion of Ni in MgCNi3 suggests that magnetic interactions are important, and the lower Tc of this three-dimensional compound-when compared to the LnNi2B2C family-contrasts with conventional ideas regarding the origins of superconductivity.     

Mutations in the polyglutamine binding protein 1 gene cause X-linked mental retardation

We found mutations in the gene PQBP1 in 5 of 29 families with nonsyndromic (MRX) and syndromic (MRXS) forms of X-linked mental retardation (XLMR). Clinical features in affected males include mental retardation, microcephaly, short stature, spastic paraplegia and midline defects. PQBP1 has previously been implicated in the pathogenesis of polyglutamine expansion diseases. Our findings link this gene to XLMR and shed more light on the pathogenesis of this common disorder.     

GABAergic inhibition of neurons in the ventral tegmental area.

Stimulation of the nucleus accumbens evokes a potent inhibition in neurons of the ventral tegmental area. GABA is likely to act as a transmitter in this descending inhibitory system.     

Parallel implementation of a multiscale edges detection algorithm

We present in this paper an implementation of a multiscale edges detection algorithm on multiprocessor using SYnDEx which is a programming environment to generate optimized distributed real-time executives. The implementation has been done on three TMS320C40 and the acceleration in comparison with one processor is 2.2.     

4-aminopyridine and barium chloride attenuate the anti-epileptic effect of carbamazepine in hippocampal slices

The exact mode of action of the anti-epileptic agent carbamazepine is unknown. In hippocampal slices in which epileptiform discharges were induced by addition of penicillin to the perfusion medium, the depressant effect of carbamazepine was attenuated by the potassium-channel blockers barium chloride (0.1 mM) and 4-aminopyridine (200 microM), which suggested that potassium fluxes might be involved in the mechanism of action of carbamazepine.     

Absence of growth by most receptor-expressing fetal thymocytes in the presence of interleukin-2

The growth of mature T cells is regulated by receptors for interleukin-2 (IL-2) and by IL-2 itself. Binding of antigen to T-cell antigen receptors induces the expression of IL-2 receptors, and binding of IL-2 to these receptors induces transferrin receptor expression and is sufficient to promote the growth of T cells for several days. However, nothing is known about the growth requirements of pre-T cells. We have therefore studied the dividing population of T-cell precursors which carry the Thy-1 surface antigen, but lack surface antigens Ly2 and L3T4; these cells are present in 14-day-old embryonic thymus. If the thymus is removed at this stage and placed in organ culture, all lymphocyte subpopulations normally present in thymuses of adult mice develop in vitro, that is, the nonfunctional Ly2+, L3T4+ population and the functional Ly2+, L3T4- and Ly2-, L3T4+ populations. We now report that, in contrast to their progeny, the early Ly2-, L3T4- cells express large amounts of IL-2 receptors, but most of them do not grow in IL-2-containing media outside the thymus. In contrast to dividing mature T cells, most fetal thymocytes express low amounts of transferrin receptors.     

Transfer of specificity by murine alpha and beta T-cell receptor genes

T-cell receptor alpha- and beta-chain genes were isolated from a class I major histocompatibility complex-restricted cytotoxic T-cell clone and transferred by protoplast fusion into another cytolytic T-cell clone of different specificity. Expression of the transfected alpha and beta genes endowed the recipient cell with the specificity of the donor cell.     

Parental origin of chromosomes involved in the translocation t(9;22).

Functionally equivalent genetic maternal can be labelled by an epigenetic marking process and used differentially depending on whether its origin is maternal or paternal. This phenomenon is known as genomic imprinting and is manifested at either the chromosomal or gene level. Genomic imprinting seems to play an important role in cancer predisposition syndromes, and phenotypic consequences are evident in constitutional deletion syndromes and uniparental disomies. Moreover, there seems to be a preferential retention of paternal alleles in sporadic tumours such as Wilms' tumour, rhabdomyosarcoma, osteosarcoma and retinoblastoma. To investigate whether chromosomes involved in acquired abnormalities of haematologic neoplasms show a similar 'parent of origin' bias, we studied the inheritance of the translocated chromosomes 9 and 22 in cases of Philadelphia-chromosome-positive leukaemia, using unique specific chromosome band polymorphisms. Here we show that the translocated chromosome 9 was of paternal origin, whereas the translocated chromosomes 22 were derived exclusively from the maternal copy, in 11 cases with reliable polymorphisms. Our data therefore provide evidence that imprinting phenomena may play an important role in acquired tumour-specific chromosome rearrangements.