Stem–loop binding protein expressed in growing oocytes is required for accumulation of mRNAs encoding histones H3 and H4 and for early embryonic development in the mouse

AbstractGrowing oocytes accumulate mRNAs and proteins that support early embryogenesis. Among the most abundant of these maternal factors are the histones. Histone mRNA accumulation and translation are mainly restricted to S-phase in somatic cells, and the mechanism by which oocytes produce histones is unknown. In somatic cells, replication-dependent histone synthesis requires the stem–loop binding protein (SLBP). SLBP is expressed during S-phase, binds to the 3′-untranslated region of non-polyadenylated transcripts encoding the histones, and is required for their stabilization and translation. SLBP is expressed in oocytes of several species, suggesting a role in histone synthesis. To test this, we generated transgenic mice whose oocytes lack SLBP. mRNAs encoding histones H3 and H4 failed to accumulate in these oocytes. Unexpectedly, mRNAs encoding H2A and H2B were little affected. Embryos derived from SLBP-depleted oocytes reached the 2-cell stage, but most then became arrested. Histones H3 and H4, but not H2A or H2B, were substantially reduced in these embryos. The embryos also expressed high levels of γH2A.X. Injection of histones into SLBP-depleted embryos rescued them from developmental arrest. Thus, SLBP is an essential component of the mechanism by which growing oocytes of the mouse accumulate the histones that support early embryonic development

Measuring the refractive index dispersion of (un)pigmented biological tissues by Jamin-Lebedeff interference microscopy

Jamin-Lebedeff interference microscopy is a powerful technique for measuring the refractive index of microscopically-sized solid objects. This method was classically used for transparent objects immersed in various refractive-index matching media by applying light of a certain predesigned wavelength. In previous studies, we demonstrated that the Jamin-Lebedeff microscopy approach can also be utilized to determine the refractive index of pigmented media for a wide range of wavelengths across the visible spectrum. The theoretical basis of the extended method was however only precise for a single wavelength, dependent on the characteristics of the microscope setup. Using Jones calculus, we here present a complete theory of Jamin-Lebedeff interference microscopy that incorporates the wavelength-dependent correction factors of the half- and quarter-wave plates. We show that the method can indeed be used universally in that it allows the assessment of the refractive index dispersion of both unpigmented and pigmented microscopic media. We illustrate this on the case of the red-pigmented wing of the damselfly Hetaerina americana and find that very similar refractive indices are obtained whether or not the wave-plate correction factors are accounted for. (C) 2019 Author(s)

Experimental study of the transport of coherent interacting matter-waves in a 1D random potential induced by laser speckle

We present a detailed analysis of the 1D expansion of a coherent interacting matterwave (a Bose-Einstein condensate) in the presence of disorder. A 1D random potential is created via laser speckle patterns. It is carefully calibrated and the self-averaging properties of our experimental system are discussed. We observe the suppression of the transport of the BEC in the random potential. We discuss the scenario of disorder-induced trapping taking into account the radial extension in our experimental 3D BEC and we compare our experimental results with the theoretical predictions

Minimal Decomposition of a Digital Surface into Digital Plane Segments Is NP-Hard

Abstract. This paper deals with the complexity of the decomposition of a digital surface into digital plane segments (DPS for short). We prove that the decision problem (does there exist a decomposition with less than k DPS?) is NP-complete, and thus that the optimisation problem (finding the minimal number of DPS) is NP-hard. The proof is based on a polynomial reduction of any instance of the well-known 3-SAT problem to an instance of the digital surface decomposition problem. A geometric model for the 3-SAT problem is proposed.

Quasi-stationary regime of a branching random walk in presence of an absorbing wall

A branching random walk in presence of an absorbing wall moving at a constant velocity $v$ undergoes a phase transition as the velocity $v$ of the wall varies. Below the critical velocity $v_c$, the population has a non-zero survival probability and when the population survives its size grows exponentially. We investigate the histories of the population conditioned on having a single survivor at some final time $T$. We study the quasi-stationary regime for $v<v_c$ when $T$ is large. To do so, one can construct a modified stochastic process which is equivalent to the original process conditioned on having a single survivor at final time $T$. We then use this construction to show that the properties of the quasi-stationary regime are universal when $v\to v_c$. We also solve exactly a simple version of the problem, the exponential model, for which the study of the quasi-stationary regime can be reduced to the analysis of a single one-dimensional map.Comment: 2 figures, minor corrections, one reference adde

On the Language of Standard Discrete Planes and Surfaces

International audienceA standard discrete plane is a subset of Z^3 verifying the double Diophantine inequality mu =< ax+by+cz < mu + omega, with (a,b,c) != (0,0,0). In the present paper we introduce a generalization of this notion, namely the (1,1,1)-discrete surfaces. We first study a combinatorial representation of discrete surfaces as two-dimensional sequences over a three-letter alphabet and show how to use this combinatorial point of view for the recognition problem for these discrete surfaces. We then apply this combinatorial representation to the standard discrete planes and give a first attempt of to generalize the study of the dual space of parameters for the latter [VC00]

Naive Planes as Discrete Combinatorial Surfaces

International audienc