Low-temperature specific heat of the heavy-fermion superconductor PrOs4Sb12.

We report the magnetic field dependence of the specific-heat C of single crystals of the first Pr-based heavy-fermion superconductor Pr(Os4Sb12. The variation of C at low temperature and the magnetic phase diagram inferred from C, the resistivity and magnetization provide compelling evidence of a doublet ground state. Two distinct superconducting anomalies in C indicate an unconventional superconducting state, where the splitting may arise from a weak lifting of the ground state degeneracy. In combination this identifies Pr(Os4Sb12 as a strong contender for quadrupolar pairing, i.e., superconductivity that is neither electron-phonon nor magnetically mediated.

Early mesodermal phenotypes in splotch suggest a role for Pax3 in the formation of epithelial somites.

The paired box containing transcription factor Pax3 is a crucial regulator of dermomyotome and muscle development. However, the allelic series of Pax3/Splotch mutants also displays characteristic vertebral column malformations, which do not result from defective dorsoventral somite pattern. Rather, vertebral column and sclerotomal phenotypes are reminiscent of the phenotypes observed in the segmentation/somitogenesis mutants rachiterata and pudgy. Moreover, rostrocaudal somite pattern and somitic boundaries are disturbed in Splotch as monitored by the expression of Uncx4.1 and Lunatic fringe. Alterations in EphA4, Dll1, and Uncx4.1 expression are evident already in the condensing paraxial mesoderm, correlating with the first phase of Pax3 expression before and during somite formation. This finding suggests an early function of Pax3 during the formation of epithelial somites.

The metallochaperone Atox1 plays a critical role in perinatal copper homeostasis.

Copper plays a fundamental role in the biochemistry of all aerobic organisms. The delivery of this metal to specific intracellular targets is mediated by metallochaperones. To elucidate the role of the metallochaperone Atox1, we analyzed mice with a disruption of the Atox1 locus. Atox1(-/-) mice failed to thrive immediately after birth, with 45% of pups dying before weaning. Surviving animals exhibited growth failure, skin laxity, hypopigmentation, and seizures because of perinatal copper deficiency. Maternal Atox1 deficiency markedly increased the severity of Atox1(-/-) phenotype, resulting in increased perinatal mortality as well as severe growth retardation and congenital malformations among surviving Atox1(-/-) progeny. Furthermore, Atox1-deficient cells accumulated high levels of intracellular copper, and metabolic studies indicated that this defect was because of impaired cellular copper efflux. Taken together, these data reveal a direct role for Atox1 in trafficking of intracellular copper to the secretory pathway of mammalian cells and demonstrate that this metallochaperone plays a critical role in perinatal copper homeostasis.

Bodenin: a novel murine gene expressed in restricted areas of the brain.

A gene trap screen designed to isolate novel mouse genes involved in nervous system development was performed. Here, we describe the isolation and characterization of a novel gene, bodenin, which is expressed in restricted areas of the brain. beta-Galactosidase marker gene activity was detected in the embryo at the start of organogenesis (embryonic day 8.5; E8.5). Staining gradually became stronger until E12.5, when embryos exhibited widespread expression. In brains of newborn and adult mice, beta-galactosidase staining was confined predominantly to forebrain structures. Transcriptional activity was also observed in kidney, liver, lung, heart, skeletal muscle, and testes. Part of the trapped gene was isolated by 5'-rapid amplification of cDNA ends (5'-RACE). Isolation and sequencing of the complete cDNA revealed an unknown gene encoding a 200 amino acid protein. Comparison with published sequences showed 94% amino acid identity to a human integrin cytoplasmic domain-associated protein. Mice homozygous for the mutation were viable and did not exhibit any obvious abnormal phenotype. However, concealed phenotypic abnormalities cannot be excluded. The lack of readily visible abnormalities may also be due to functional compensation or to the production of low levels of wild-type protein in mice homozygous for the gene trap vector insertion. Nevertheless, the restricted expression of bodenin in the brain of newborn and adult mice suggests a role for this novel gene in the developing and mature central nervous system.

SIV- and HIV-2-neutralising antibodies in infected macaques measured by a novel and simple neutralisation test based on a non-commercial antigen-ELISA.

A method for the measurement of neutralising antibodies (nab) directed against SIVmac or HIV-2 was developed. The assay is based on antigen detection using a non-commercial enzyme-linked immunosorbent assay (ELISA). Studies were carried out to determine the influence of the test conditions on the nab titre. The sensitivity of the assay depended mainly on the virus dose and the length of incubation of the serum-virus-mixture. Prolongation of the culture time from 9 to 11 days increased the validity of the results. Applying this neutralisation assay on sequential serum samples from SIV mac- or HIV-2ben-infected macaques, a considerable variation was found in nab titres between individual animals. Whereas after infection with SIVmac, in vitro-neutralisation seems to correlate with protection against disease, and the lower pathogenity of HIV-2ben in macaques compared with SIVmac is not due to the differences in nab titres.

Generation, characterization and cross-reactivities of monoclonal antibodies against the p24 core protein and the gp130 envelope glycoprotein of HIV-2ben.

The purpose of this study was to characterize antigenic determinants on structural polypeptides of human immunodeficiency virus type 2 (HIV-2ben). Therefore, three HIV-2-specific monoclonal antibodies (mAbs) against the p24 core protein (gag) and one mAb against the gp130 envelope glycoprotein (env) were produced. In addition to p24 the anti-core mAbs recognized the primary translation product of the viral gag gene p55 and an intermediate cleavage product p41. Core mAbs cross-reacted with another HIV-2 isolate (HIV-2rod), and several simian immunodeficiency viruses (SIVagm TYO7 and SIVmac), but not with SIVmnd and the HIV-1 isolates investigated (HIV-1han and HIV-1lai). The env mAb cross-reacted with HIV-2rod and SIVmac but not with SIVagm, SIVmnd or HIV-1. In competition assays and with epitope mapping possible binding sites for the mAbs were identified. The processing of HIV-2 core proteins is compared in retrovirus-infected T cell lines and during the expression by recombinant vaccinia virus. Finally, the mAb XIV DC10 which recognized a highly conserved epitope could be useful for an assay to detect HIV-1 and HIV-2 simultaneously. II D8 is the first mAb raised against HIV-2 env glycoprotein.

Identification of a gag protein epitope conserved among all four groups of primate immunodeficiency viruses by using monoclonal antibodies.

Five monoclonal antibodies (MAbs) were raised against the gag proteins of simian immunodeficiency virus (SIV) from African green monkey (SIVagmTYO-7). Two MAbs reacted with the matrix protein p17 and the other three with the core protein p24. Studies on the cross-reactivity of the MAbs revealed that the anti-p24 MAbs detected an epitope shared by the viruses belonging to the human immunodeficiency virus type 2 (HIV-2)/SIVmac group and SIVagmTYO-7 and SIVagmTYO-5. The anti-p17 MAbs recognized an epitope present on all these viruses and on SIVagmTYO-1, HIV-1 and SIVmnd. This finding demonstrates for the first time that the matrix protein, p17 or p18, respectively, of all nine HIV and SIV isolates tested in this study expresses at least one conserved immunogenic epitope recognized serologically. By using synthetic peptides, this epitope was identified at the N terminus of p17. Furthermore, this epitope was analysed by multiple sequence alignments of the peptide with homologous sequences of HIV and SIV p17.