Efficient delivery of Cre-recombinase to neurons in vivo and stable transduction of neurons using adeno-associated and lentiviral vectors

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.     

Observation of optical Ramsey interference fringes in collinear ion beam-laser beam interaction by Doppler switching

We report the observation of optical Ramsey interference fringes in collinear ion beam-laser beam interaction. The analogue of separated fields is created by Doppler switching the ions in two successive zones of the common beam path. New conditions to study quantum interference effects are offered by this method.     

High-energy hadron-hadron collisions and internal hadron structure

As shown by many authors, central particle emission in pp collisions at centre-of-mass energies ? 20 GeV can be described in terms of independent cluster production. In ref. [1] this process has been related to the quark-gluon picture of nucleon structure. The present paper carries this relation further and links the leading particle spectrum of non-diffractive hadron-hadron collisions to the x distribution of quarks in the hadron. Thus, the flat leading particle spectrum, as observed in non-diffractive pp collisions, is found to be naturally related to the steeply falling x distribution of quarks in the nucleon, as deduced from the structure functions measured in deep inelastic scattering of electrons and neutrinos on nucleons. Our analysis is extended to meson-nucleon collisions and leads to a prediction of the general shape of the quark x distribution in a meson.     

An analysis of the structure of the iridium (111) surface by low-energy electron diffraction

Elastic low-energy electron diffraction (LEED) intensity versus voltage (I-V) measurements for the clean Ir(111) surface have been obtained. Seven specular I-V spectra were measured from 15 to 975 eV at incident angles from 7° to 62.5° relative to the surface normal. The outermost atomic layer spacing of the unreconstructed Ir(111) surface was determined both by the convolution-transform method we have presented previously (including certain convenient modifications) and by dynamical calculations. Results from the analysis of the I-V spectra by the convolution-transform method indicate that the outermost Ir(111) layer spacing is either unrelaxed or contracts by 4% of its bulk value depending upon whether the θ=7° data or the θ = 25° data are used. In agreement with this, the dynamical calculations show that the outermost Ir(111) layer spacing contracts by 2.5± 5% and, in addition, that the registry of the first layer of the crystal surface is not shifted, maintaining the fcc structure.     

Inelastic diffraction in the quark-glue model

Diffractive dissociation of hadrons is related to the quark-glue picture of their structure. It is shown that the quark-glue model can produce sufficiently large variations of opacities for diffractive eigenstates to account for the experimental value of diffractive cross sections if unitarity is saturated in central glue-glue collisions. This requirement simplifies the collision picture and provides a natural explanation for the observed energy independence of proton opacity in central pp collisions.     

Criticality in the (2+1)-dimensional compact Higgs model and fractionalized insulators

We use a novel method of computing the third moment M3 of the action of the (2+1)-dimensional compact Higgs model in the adjoint representation with q=2 to extract correlation length and specific heat exponents nu and alpha without invoking hyperscaling. Finite-size scaling analysis of M3 yields the ratios (1+alpha)/nu and 1/nu separately. We find that alpha and nu vary along the critical line of the theory, which however exhibits a remarkable resilience of Z2 criticality. We propose this novel universality class to be that of the quantum phase transition from a Mott-Hubbard insulator to a charge-fractionalized insulator in two spatial dimensions.     

Positive integer solutions of the diophantine equation x 2 − L n xy + (−1) n y 2 = ±5 r

In this paper, we consider the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r and determine the values of n for which the equation has positive integer solutions x and y. Moreover, we give all positive integer solutions of the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r when the equation has positive integer solutions.     

Single-molecule resolution of an organometallic intermediate in a surface-supported Ullmann coupling reaction

We have studied the organometallic intermediate of a surface-supported Ullmann coupling reaction from 4, 4″-dibromo-p-terphenyl to poly(para-phenylene) by scanning tunneling microscopy/spectroscopy and density functional theory calculations. Our study reveals at a single-molecular level that the intermediate consists of biradical terphenyl (ph)(3) units that are connected by single Cu atoms through C-Cu-C bridges. Upon further increasing the temperature, the neighboring biradical (ph)(3) units are coupled by C-C bonds forming poly(para-phenylene) oligomers while the Cu atoms are released.     

Single and double dissociation in πp collisions at 11 and 16 GeV/c

The reactions π⁻p → 2π⁻π⁺p, π⁻p → 2π⁻π⁺π^op and π⁻p → 2π⁻2π⁺n are analysed at 11 and 16 GeV/c using longitudinal phase space (LPS) plots. The weighted LPS distributions for π⁻p → 2π⁻π⁺p is dominated by two well separated structures corresponding to single diffraction dissociation of the pion, π⁻p → (2π⁻π⁺)p, and of the proton, π⁻p → π⁻(π⁻π⁺p). The former is more abundant than the latter, and both are approximately constant with energy. In contrast, processes of type π⁻p → (2π)(πp) decrease with increasing energy.

In the five-body reactions the weighted LPS distribution reveals especially at 16 GeV/c a maximum for single dissociation of the proton into 3πp, namely π⁻p → π⁻(π⁻π⁺π^op); this process is likely to be diffractive. The neutron channel has a corresponding maximum displaced toward a multiperipheral configuration π⁻p → π⁻(π⁻2π⁺)n. Another strong maximum corresponds to the pion dissociation π⁻p → (2π⁻π⁺π^o)p. This is interpreted to be an ω-exchange process because no analogous structure occurs in π⁻p → (2π⁻2π⁺)n. Finally, a broad structure reveals double dissociation of both incident particles; it occurs in the two channels π⁻p → (2π⁻π⁺)(π^op) and π⁻p → (2π⁻π⁺)(π⁺n), being stronger in the latter. Further analysis of this process in terms of isospin exchange suggests that it is partially diffractive. Factorization is also discussed.

An appendix gives general aspects of the LPS analysis for the asymptotic study of n-body collisions at very high energy.