Sur certaines conditions de la transformation du type antigénique et de l'équipement enzymatique d'un colibacille,sous l'effet d'un principe inducteur de nature thymonucléique issu d'un autre colibacille (mutation « dirigée »)

Summary The transformation of antigenic and enzymatic properties of a bacteria can be produced by the action of an inductor thymonucleic factor, which comes from a related bacteria. However, this transformation is only possible when the bacteria which must undergo the mutation dirigée is in a state of pronounced instability, the determinism of which is still unknown. We find to-day the greatest difficulties to isolate, without destroying it, the inductor factor, because it is very sensitive to bacterial enzyms and to the delayed action of acids and bases.     

Neocortical transplants in the rat brain: an ultrastructural study

Electron microscopic analysis of neocortical transplants in the cerebellum of the host animals showed that the nerve cells, glial cells, and neuropil of the transplants were normal. These transplants showed anatomical integration with the host brain through various regions of interface. Neuropil interfaces were found to have a high density of synaptic profiles, and medullary interfaces had a very small number of synaptic profiles.     

Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser

Since the invention of the laser more than 50 years ago, scientists have striven to achieve amplification on atomic transitions of increasingly shorter wavelength. The introduction of X-ray free-electron lasers makes it possible to pump new atomic X-ray lasers with ultrashort pulse duration, extreme spectral brightness and full temporal coherence. Here we describe the implementation of an X-ray laser in the kiloelectronvolt energy regime, based on atomic population inversion and driven by rapid K-shell photo-ionization using pulses from an X-ray free-electron laser. We established a population inversion of the Kα transition in singly ionized neon at 1.46 nanometres (corresponding to a photon energy of 849 electronvolts) in an elongated plasma column created by irradiation of a gas medium. We observed strong amplified spontaneous emission from the end of the excited plasma. This resulted in femtosecond-duration, high-intensity X-ray pulses of much shorter wavelength and greater brilliance than achieved with previous atomic X-ray lasers. Moreover, this scheme provides greatly increased wavelength stability, monochromaticity and improved temporal coherence by comparison with present-day X-ray free-electron lasers. The atomic X-ray lasers realized here may be useful for high-resolution spectroscopy and nonlinear X-ray studies.     

Tumour suppressor RNF43 is a stem-cell E3 ligase that induces endocytosis of Wnt receptors

LGR5+ stem cells reside at crypt bottoms, intermingled with Paneth cells that provide Wnt, Notch and epidermal growth factor signals. Here we find that the related RNF43 and ZNRF3 transmembrane E3 ubiquitin ligases are uniquely expressed in LGR5+ stem cells. Simultaneous deletion of the two genes encoding these proteins in the intestinal epithelium of mice induces rapidly growing adenomas containing high numbers of Paneth and LGR5+ stem cells. In vitro, growth of organoids derived from these adenomas is arrested when Wnt secretion is inhibited, indicating a dependence of the adenoma stem cells on Wnt produced by adenoma Paneth cells. In the HEK293T human cancer cell line, expression of RNF43 blocks Wnt responses and targets surface-expressed frizzled receptors to lysosomes. In the RNF43-mutant colorectal cancer cell line HCT116, reconstitution of RNF43 expression removes its response to exogenous Wnt. We conclude that RNF43 and ZNRF3 reduce Wnt signals by selectively ubiquitinating frizzled receptors, thereby targeting these Wnt receptors for degradation.     

Heterogeneous pathways and timing of factor departure during translation initiation

The initiation of translation establishes the reading frame for protein synthesis and is a key point of regulation. Initiation involves factor-driven assembly at a start codon of a messenger RNA of an elongation-competent 70S ribosomal particle (in bacteria) from separated 30S and 50S subunits and initiator transfer RNA. Here we establish in Escherichia coli, using direct single-molecule tracking, the timing of initiator tRNA, initiation factor 2 (IF2; encoded by infB) and 50S subunit joining during initiation. Our results show multiple pathways to initiation, with orders of arrival of tRNA and IF2 dependent on factor concentration and composition. IF2 accelerates 50S subunit joining and stabilizes the assembled 70S complex. Transition to elongation is gated by the departure of IF2 after GTP hydrolysis, allowing efficient arrival of elongator tRNAs to the second codon presented in the aminoacyl-tRNA binding site (A site). These experiments highlight the power of single-molecule approaches to delineate mechanisms in complex multicomponent systems.     

Design of Magnetic RF Inductor in CMOS

Traditional planar inductors in Radio Frequency (RF) Integrated Circuits (ICs) are plagued by large areas, low quality, and low frequencies. This paper describes a magnetic-based CMOS-compatible RF in-ductor. Magnetic-core inductors with various ferrite-filled structures, spiral structures, and magnetic material permeabilities were simulated to show that this inductor greatly improves the inductance by up to 97% and quality factor by 18.6% over a multi-GHz frequency range. The results indicate that the inductor is a very promising and viable solution to realize miniature, high quality, and high frequency on-chip inductors for high-end RF ICs.     

A novel <Emphasis Type=Italic>in vitro</Emphasis> angiogenesis model based on a microfluidic device

Angiogenesis is very important for many physiological and pathological processes. However, the molecular mechanisms of angiogenesis are unclear. To elucidate the molecular mechanisms of angiogenesis and to develop treatments for angiogenesis-dependent diseases, it is essential to establish a suitable in vitro angiogenesis model. In this study, we created a novel in vitro angiogenesis model based on a microfluidic device. Our model provides an in vivo-like microenvironment for endothelial cells (ECs) cultures and monitors the response of ECs to changes in their microenvironment in real time. To evaluate the potential of this microfluidic device for researching angiogenesis, the effects of pro-angiogenic factors on ECs proliferation, migration and tube-like structure formation were investigated. Our results showed the proliferation rate of ECs in 3D matrix was significantly promoted by the pro-angiogenic factors (with an increase of 59.12%). With the stimulation of pro-angiogenic factors gradients, ECs directionally migrated into the Matrigel from low concentrations to high concentrations and consequently formed multi-cell chords and tube-like structures. These results suggest that the device can provide a suitable platform for elucidating the mechanisms of angiogenesis and for screening pro-angiogenic or anti-angiogenic drugs for angiogenesis-dependent diseases.