Action d'un hépatome ascitique du rat sur les acides nucléiques du pancréas et du rein

Summary Animals having an ascites hepatoma show an increase in the incorporation of P³² into ribonucleic acid and desoxyribonucleic acid of the pancreas, whereas no change is seen in the kidneys. The variations noted in the pancreas may be compared with those observed previously in the liver and the adrenals. It can therefore be presumed that a substance which stimulates biosynthesis or disrupts the normal metabolic balance is produced by the ascites cells.

---

---

Travail effectué avec l'aide matérielle de l'Institut National d'Hygiène.     

Histochemical study of dissociated nerve cells from embryonic chick cerebral hemispheres in flask cultures

Zusammenfassung Die Differenzierung von dissoziierten Grosshirnneuronen in Plastikflaschenkulturen wurde mit histochemischen Methoden, Nisslfärbung, Silberimprägnation der Nervenfasern und Acetylcholinesteraseaktivität untersucht.

---

---

with the technical assistance ofM. F. Knoetgen

---

Chargée de Recherche au C.N.R.S.     

Opiate receptor sites in neuronal and glial cell lines in culture]

A stereospecific saturable high affinity binding of 3H-naloxone has been found in 3 glial and 2 neuronal cell lines. Kinetic study of binding seems to indicate only one class of receptor sites in the 5 cell lines. Acute exposure to morphine (1 X 10(-5)M) concurrent with PGE1-induced stimulation of adenylate cyclase did not result in a decrease of the cAMP level in any cell line tested.     

Light echoes reveal an unexpectedly cool η Carinae during its nineteenth-century Great Eruption

η?Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightest star in our sky during its mid-nineteenth-century 'Great Eruption', but then faded from view (with only naked-eye estimates of brightness). Its eruption is unique in that it exceeded the Eddington luminosity limit for ten years. Because it is only 2.3 kiloparsecs away, spatially resolved studies of the nebula have constrained the ejected mass and velocity, indicating that during its nineteenth-century eruption, η?Car ejected more than ten solar masses in an event that released ten per cent of the energy of a typical core-collapse supernova, without destroying the star. Here we report observations of light echoes of η?Carinae from the 1838-1858 Great Eruption. Spectra of these light echoes show only absorption lines, which are blueshifted by -210?km?s(-1), in good agreement with predicted expansion speeds. The light-echo spectra correlate best with those of G2-to-G5 supergiants, which have effective temperatures of around 5,000?kelvin. In contrast to the class of extragalactic outbursts assumed to be analogues of the Great Eruption of η?Carinae, the effective temperature of its outburst is significantly lower than that allowed by standard opaque wind models. This indicates that other physical mechanisms such as an energetic blast wave may have triggered and influenced the eruption.     

Fragile X mental retardation protein interacts with TDG

Fragile X syndrome is the most common form of inherited mental retardation disease, resulting from absent of expression of its disease geneFMR1. To study the function of the fragile X mental retardation protein (FMRP) through protein/protein interaction, a mouse embryo cDNA library was screened by the yeast two-hybrid system. A clone was found to interact specifically with FMRP. The cDNA of this clone (Genbank accession number af 102875) encoded a protein highly homologous to human G/T mismatch-specific DNA thymine glycosylase (hTDG). Interactions between various alternatively spliced FMRP isoforms and a series of mTDG deletion proteins were further studied in the yeast two-hybrid system and their interaction amino acid regions were determined. Interaction between FMRP and TDG existed inside exon 13 of FMRP (amino acid residue 397–425) and around amino acid residue 122–346 of TDG. These results will be helpful to the study of the biological role of FMRP.     

Mutant mitochondrial thymidine kinase in mitochondrial DNA depletion myopathy.

The mitochondrial deoxyribonucleotide (dNTP) pool is separated from the cytosolic pool because the mitochondria inner membrane is impermeable to charged molecules. The mitochondrial pool is maintained by either import of cytosolic dNTPs through dedicated transporters or by salvaging deoxynucleosides within the mitochondria; apparently, enzymes of the de novo dNTP synthesis pathway are not present in the mitochondria. In non-replicating cells, where cytosolic dNTP synthesis is down-regulated, mtDNA synthesis depends solely on the mitochondrial salvage pathway enzymes, the deoxyribonucleosides kinases. Two of the four human deoxyribonucleoside kinases, deoxyguanosine kinase (dGK) and thymidine kinase-2 (TK2), are expressed in mitochondria. Human dGK efficiently phosphorylates deoxyguanosine and deoxyadenosine, whereas TK2 phosphorylates deoxythymidine, deoxycytidine and deoxyuridine. Here we identify two mutations in TK2, histidine 90 to asparagine and isoleucine 181 to asparagine, in four individuals who developed devastating myopathy and depletion of muscular mitochondrial DNA in infancy. In these individuals, the activity of TK2 in muscle mitochondria is reduced to 14-45% of the mean value in healthy control individuals. Mutations in TK2 represent a new etiology for mitochondrial DNA depletion, underscoring the importance of the mitochondrial dNTP pool in the pathogenesis of mitochondrial depletion.     

Mutations in VPS33B, encoding a regulator of SNARE-dependent membrane fusion, cause arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome

ARC syndrome (OMIM 208085) is an autosomal recessive multisystem disorder characterized by neurogenic arthrogryposis multiplex congenita, renal tubular dysfunction and neonatal cholestasis with bile duct hypoplasia and low gamma glutamyl transpeptidase (gGT) activity. Platelet dysfunction is common. Affected infants do not thrive and usually die in the first year of life. To elucidate the molecular basis of ARC, we mapped the disease to a 7-cM interval on 15q26.1 and then identified germline mutations in the gene VPS33B in 14 kindreds with ARC. VPS33B encodes a homolog of the class C yeast vacuolar protein sorting gene, Vps33, that contains a Sec1-like domain important in the regulation of vesicle-to-target SNARE complex formation and subsequent membrane fusion.     

Tonks-Girardeau gas of ultracold atoms in an optical lattice

Strongly correlated quantum systems are among the most intriguing and fundamental systems in physics. One such example is the Tonks-Girardeau gas, proposed about 40 years ago, but until now lacking experimental realization; in such a gas, the repulsive interactions between bosonic particles confined to one dimension dominate the physics of the system. In order to minimize their mutual repulsion, the bosons are prevented from occupying the same position in space. This mimics the Pauli exclusion principle for fermions, causing the bosonic particles to exhibit fermionic properties. However, such bosons do not exhibit completely ideal fermionic (or bosonic) quantum behaviour; for example, this is reflected in their characteristic momentum distribution. Here we report the preparation of a Tonks-Girardeau gas of ultracold rubidium atoms held in a two-dimensional optical lattice formed by two orthogonal standing waves. The addition of a third, shallower lattice potential along the long axis of the quantum gases allows us to enter the Tonks-Girardeau regime by increasing the atoms' effective mass and thereby enhancing the role of interactions. We make a theoretical prediction of the momentum distribution based on an approach in which trapped bosons acquire fermionic properties, finding that it agrees closely with the measured distribution.