Oocytes prevent cumulus cell apoptosis by maintaining a morphogenic paracrine gradient of bone morphogenetic proteins

© The Company of Biologists Ltd 2005Paracrine factors secreted by the oocyte regulate a broad range of cumulus cell functions. Characteristically, cumulus cells have a low incidence of apoptosis and we proposed that this is due to oocyte-secreted factors acting in an anti-apoptotic manner. Bovine cumulus-oocyte complexes (COC) were aspirated from abattoir-derived ovaries and oocytectomized (OOX) by microsurgical removal of the oocyte. OOX were treated with doses of either denuded oocytes (DO) or various growth factors for 24 hours (± rFSH; 0.1 IU/ml). Proportions of apoptotic cumulus cells were assessed using TUNEL and laser confocal scanning microscopy followed by image analysis. Quantification of Bcl-2 and Bax proteins in OOX was undertaken by western analysis. Oocyte removal led to a significant increase in cumulus cell apoptosis compared with COC controls (35% versus 9% TUNEL positive, respectively; P<0.001). Levels of OOX apoptosis were significantly reversed (P<0.001) in a dose-dependent manner when co-cultured with oocytes. Furthermore, the anti-apoptotic effect of oocyte-secreted factors followed a gradient from the site of the oocyte(s). Growth differentiation factor 9 (GDF9) had no significant effect on cumulus cell apoptosis. By contrast, cumulus cell apoptosis was significantly (P<0.001) reduced by bone morphogenetic proteins (BMP) 15, 6 or 7. Accordingly, levels of antiapoptotic Bcl-2 were high in OOX+DO and OOX+BMP15 and low with OOX+GDF9 or OOX alone, whereas the reverse was observed for pro-apoptotic Bax. DO, BMP15 and BMP6 were also able to protect cumulus cells from undergoing apoptosis induced by staurosporine. FSH partially prevented apoptosis in all treatment groups (P<0.001). Follistatin and a BMP6 neutralizing antibody, which antagonized the anti-apoptotic effects of BMP15 and BMP6, respectively, whether alone or combined, blocked ~50% of the anti-apoptotic actions of oocytes. These results are the first to demonstrate that oocyte-secreted factors, and particularly BMP15 and BMP6, maintain the low incidence of cumulus cell apoptosis by establishing a localized gradient of bone morphogenetic proteins.Tamer S. Hussein, David A. Froiland, Fred Amato, Jeremy G. Thompson and Robert B

Quantum process tomography of a controlled-NOT gate

We demonstrate complete characterization of a two-qubit entangling process - a linear optics controlled-NOT gate operating with coincident detection - by quantum process tomography. We use maximum-likelihood estimation to convert the experimental data into a physical process matrix. The process matrix allows accurate prediction of the operation of the gate for arbitrary input states, and calculation of gate performance measures such as the average gate fidelity, average purity and entangling capability of our gate, which are 0.90, 0.83 and 0.73, respectively.Comment: 4 pages, 2 figures. v2 contains new data corresponding to improved gate operation. Figure quality slightly reduced for arXi

Aging in K1−x_{1-x}Lix_xTa03_3: a domain growth interpretation

The aging behaviour of the a.c. susceptibility of randomly substituted K$_{1-x}$Li$_x$Ta0$_3$ crystals reveals marked differences with spin-glasses in that cooling rate effects are very important. The response to temperature steps (including temperature cycles) was carefully studied. A model based on thermally activated domain growth accounts for all the experimental results, provided one allows for a large distribution of pinning energies, in such a way that `slow' and `fast' domains coexist. Interesting similarities with deeply supercooled liquids are underlined.Comment: 4 pages. Preprint LPTENS/9820, submitted to Phys. Rev. Let

Experimental demonstration of Shor's algorithm with quantum entanglement

Shor's powerful quantum algorithm for factoring represents a major challenge in quantum computation and its full realization will have a large impact on modern cryptography. Here we implement a compiled version of Shor's algorithm in a photonic system using single photons and employing the non-linearity induced by measurement. For the first time we demonstrate the core processes, coherent control, and resultant entangled states that are required in a full-scale implementation of Shor's algorithm. Demonstration of these processes is a necessary step on the path towards a full implementation of Shor's algorithm and scalable quantum computing. Our results highlight that the performance of a quantum algorithm is not the same as performance of the underlying quantum circuit, and stress the importance of developing techniques for characterising quantum algorithms.Comment: 4 pages, 5 figures + half-page additional online materia

The pupil's response to affective pictures: Role of image duration, habituation, and viewing mode

The pupil has been shown to be sensitive to the emotional content of stimuli. We examined this phenomenon by comparing fearful and neutral images carefully matched in the domains of luminance, image contrast, image color, and complexity of content. The pupil was more dilated after viewing affective pictures, and this effect was (a) shown to be independent of the presentation time of the images (from 100–3,000 ms), (b) not diminished by repeated presentations of the images, and (c) not affected by actively naming the emotion of the stimuli in comparison to passive viewing. Our results show that the emotional modulation of the pupil is present over a range of variables that typically vary from study to study (image duration, number of trials, free viewing vs. task), and encourages the use of pupillometry as a measure of emotional processing in populations where alternative techniques may not be appropriate

How to simulate a quantum computer using negative probabilities

The concept of negative probabilities can be used to decompose the interaction of two qubits mediated by a quantum controlled-NOT into three operations that require only classical interactions (that is, local operations and classical communication) between the qubits. For a single gate, the probabilities of the three operations are 1, 1, and -1. This decomposition can be applied in a probabilistic simulation of quantum computation by randomly choosing one of the three operations for each gate and assigning a negative statistical weight to the outcomes of sequences with an odd number of negative probability operations. The exponential speed-up of a quantum computer can then be evaluated in terms of the increase in the number of sequences needed to simulate a single operation of the quantum circuit.Comment: 11 pages, including one figure and one table. Full paper version for publication in Journal of Physics A. Clarifications of basic concepts and discussions of possible implications have been adde

Non-Abelian anyonic interferometry with a multi-photon spin lattice simulator

Recently a pair of experiments demonstrated a simulation of Abelian anyons in a spin network of single photons. The experiments were based on an Abelian discrete gauge theory spin lattice model of Kitaev. Here we describe how to use linear optics and single photons to simulate non-Abelian anyons. The scheme makes use of joint qutrit-qubit encoding of the spins and the resources required are three pairs of parametric down converted photons and 14 beam splitters.Comment: 13 pages, 5 figures. Several references added in v

Quantum metrology at the Heisenberg limit with ion traps

Sub-Planck phase-space structures in the Wigner function of the motional degree of freedom of a trapped ion can be used to perform weak force measurements with Heisenberg-limited sensitivity. We propose methods to engineer the Hamiltonian of the trapped ion to generate states with such small scale structures, and we show how to use them in quantum metrology applications.Comment: 10 pages, 6 figure

Schrodinger cats and their power for quantum information processing

We outline a toolbox comprised of passive optical elements, single photon detection and superpositions of coherent states (Schrodinger cat states). Such a toolbox is a powerful collection of primitives for quantum information processing tasks. We illustrate its use by outlining a proposal for universal quantum computation. We utilize this toolbox for quantum metrology applications, for instance weak force measurements and precise phase estimation. We show in both these cases that a sensitivity at the Heisenberg limit is achievable.Comment: 10 pages, 5 figures; Submitted to a Special Issue of J. Opt. B on "Fluctuations and Noise in Photonics and Quantum Optics" (Herman Haus Memorial Issue

Minimum error discrimination of Pauli channels

We solve the problem of discriminating with minimum error probability two given Pauli channels. We show that, differently from the case of discrimination between unitary transformations, the use of entanglement with an ancillary system can strictly improve the discrimination, and any maximally entangled state allows to achieve the optimal discrimination. We also provide a simple necessary and sufficient condition in terms of the structure of the channels for which the ultimate minimum error probability can be achieved without entanglement assistance. When such a condition is satisfied, the optimal input state is simply an eigenstate of one of the Pauli matrices.Comment: 8 pages, no figure