Role of androgen and gonadotrophins in the development and function of the Sertoli cells and Leydig cells: data from mutant and genetically modified mice

Development and maintenance of the male phenotype and establishment of fertility are all dependent upon the activity of the Sertoli cells and Leydig cells of the testis. This review examines the regulation and function of these cell during fetal and post-natal development. Fetal Leydig cells are sensitive to both luteinising hormone (LH) and adrenocorticotrophic hormone (ACTH) but Leydig cell function appears normal in fetal mice lacking both hormones or their receptors. Post-natally, the Sertoli cells and Leydig cells are reliant upon the pituitary gonadotrophins. Leydig cells are critically dependent on LH but follicle-stimulating hormone (FSH), presumably acting through the Sertoli cell, can also affect Leydig cell function. Testosterone secreted by the Leydig cells acts with FSH to stimulate Sertoli cell activity and spermatogenesis. Study of animals lacking FSH-receptors and androgen-receptors shows that both hormones can act to maintain the meiotic germ cell population but that androgens are critical for completion of meiosis

Apparent vernalization requirement of high yielding spring wheat

Non-Peer ReviewedControlled environment studies have demonstrated that the high yield potential of certain spring wheat (Triticum aestivum L.) cultivars may result from a moderate vernalization requirement. The objective of this study was to determine whether apparent vernalization responses of cultivars could be detected when comparing the development of early and late-seeded crops. The effect of delayed seeding on 9 or 10 spring wheat cultivars was studied at Saskatoon over a period of four years. Within years, the earliest and latest dates of seeding differed by a minimum of 22 days. Vernalization effects were apparent in 1983 and 1986 but not in 1985 and 1987. In 1983 and 1986 Growing Degree Day accumulation 14 days after seeding (GDD14) averaged 44 for the earliest date of seeding compared to 120 GDD or more for the later seeding dates. However, the GDD14 for the earliest date of seeding was 121 in 1985 and 134 in 1987. Apparent vernalization effects were manifested by higher main stem leaf number, increased spikelet production and delayed spike emergence. Cultivars were ranked in the following order for apparent vernalization sensitivity: Fielder = Pitic 62 > HY402 > HY320 > Genesis > HY912 > Leader > Glenlea > Neepawa > Katepwa > Siete Cerros > Potam. Fielder had the greatest vernalization requirement and Potam the least. On average, delayed seeding resulted in increased grain yields, but this observation was not consistent over years

A random matrix decimation procedure relating β=2/(r+1)\beta = 2/(r+1) to β=2(r+1)\beta = 2(r+1)

Classical random matrix ensembles with orthogonal symmetry have the property that the joint distribution of every second eigenvalue is equal to that of a classical random matrix ensemble with symplectic symmetry. These results are shown to be the case $r=1$ of a family of inter-relations between eigenvalue probability density functions for generalizations of the classical random matrix ensembles referred to as $\beta$-ensembles. The inter-relations give that the joint distribution of every $(r+1)$-st eigenvalue in certain $\beta$-ensembles with $\beta = 2/(r+1)$ is equal to that of another $\beta$-ensemble with $\beta = 2(r+1)$. The proof requires generalizing a conditional probability density function due to Dixon and Anderson.Comment: 19 pages, 1 figur

A sharp growth condition for a fast escaping spider's web

We show that the fast escaping set $A(f)$ of a transcendental entire function $f$ has a structure known as a spider's web whenever the maximum modulus of $f$ grows below a certain rate. We give examples of entire functions for which the fast escaping set is not a spider's web which show that this growth rate is best possible. By our earlier results, these are the first examples for which the escaping set has a spider's web structure but the fast escaping set does not. These results give new insight into a conjecture of Baker and a conjecture of Eremenko

Muon sites in PbF2 and YF3: Decohering environments and the role of anion Frenkel defects

Muons implanted into ionic fluorides often lead to a so-called F– μ –F state, in which the time evolution of the muon spin contains information about the geometry and nature of the muon site. Nuclei more distant from the muon than the two nearest-neighbor fluorine ions result in decoherence of the F– μ –F system, and this can yield additional quantitative information about the state of the muon. We demonstrate how this idea can be applied to the determination of muon sites within the ionic fluorides α − PbF 2 and YF 3 , which contain fluoride ions in different crystallographic environments. Our results can be used to distinguish between different crystal phases and provide strong evidence for the existence of anion Frenkel defects in α − PbF 2

Global patterns in the divergence between phylogenetic diversity and species richness in terrestrial birds

Aim The conservation value of sites is often based on species richness (SR).However, metrics of phylogenetic diversity (PD) reflect a community’s evolu-tionary potential and reveal the potential for additional conservation valueabove that based purely on SR. Although PD is typically correlated with SR,localized differences in this relationship have been found in different taxa.Here, we explore geographical variation in global avian PD. We identify wherePD is higher or lower than expected (from SR) and explore correlates of thosedifferences, to find communities with high irreplaceability, in terms of theuniqueness of evolutionary histories.Location Global terrestrial.Methods Using comprehensive avian phylogenies and global distributionaldata for all extant birds, we calculated SR and Faith’s PD, a widely appliedmeasure of community PD, across the terrestrial world. We modelled the rela-tionship between avian PD for terrestrial birds and its potential environmentalcorrelates. Analyses were conducted at a global scale and also for individualbiogeographical realms. Potential explanatory variables of PD included SR,long-term climate stability, climatic diversity (using altitudinal range as aproxy), habitat diversity and proximity to neighbouring realms.Results We identified areas of high and low relative PD (rPD; PD relative tothat expected given SR). Areas of high rPD were associated with deserts andislands, while areas of low rPD were associated with historical glaciation. Ourresults suggest that rPD is correlated with different environmental variables indifferent parts of the world.Main conclusions There is geographical variation in avian rPD, much ofwhich can be explained by putative drivers. However, the importance of thesedrivers shows pronounced regional variation. Moreover, the variation in avianrPD differs substantially from patterns found for mammals and amphibians.We suggest that PD adds additional insights about the irreplaceability of com-munities to conventional metrics of biodiversity based on SR, and could beusefully included in assessments of site valuation and prioritizatio

The Calogero-Sutherland Model and Polynomials with Prescribed Symmetry

The Schr\"odinger operators with exchange terms for certain Calogero-Sutherland quantum many body systems have eigenfunctions which factor into the symmetric ground state and a multivariable polynomial. The polynomial can be chosen to have a prescribed symmetry (i.e. be symmetric or antisymmetric) with respect to the interchange of some specified variables. For four particular Calogero-Sutherland systems we construct an eigenoperator for these polynomials which separates the eigenvalues and establishes orthogonality. In two of the cases this involves identifying new operators which commute with the corresponding Schr\"odinger operators. In each case we express a particular class of the polynomials with prescribed symmetry in a factored form involving the corresponding symmetric polynomials.Comment: LaTeX 2.09, 31 page

Persistent dynamics in the S = 1/2 quasi-one-dimensional chain compound Rb4Cu(MoO4)3 probed with muon-spin relaxation

We report the results of muon-spin relaxation measurements on the low-dimensional antiferromagnet Rb4Cu(MoO4)3. No long-range magnetic order is observed down to 50 mK implying a ratio TN/J < 0.005 (where J is the principal exchange strength along the spin chains) and an effective ratio of interchain to intrachain exchange of |J⊥/J | < 2 × 10−3, making the material an excellent realization of a one-dimensional quantum Heisenberg antiferromagnet. We probe the persistent spin excitations at low temperatures and find that ballistic spin transport dominates the excitations detected below 0.3 K

Expanded Vandermonde powers and sum rules for the two-dimensional one-component plasma

The two-dimensional one-component plasma (2dOCP) is a system of $N$ mobile particles of the same charge $q$ on a surface with a neutralising background. The Boltzmann factor of the 2dOCP at temperature $T$ can be expressed as a Vandermonde determinant to the power $\Gamma=q^{2}/(k_B T)$. Recent advances in the theory of symmetric and anti-symmetric Jack polymonials provide an efficient way to expand this power of the Vandermonde in their monomial basis, allowing the computation of several thermodynamic and structural properties of the 2dOCP for $N$ values up to 14 and $\Gamma$ equal to 4, 6 and 8. In this work, we explore two applications of this formalism to study the moments of the pair correlation function of the 2dOCP on a sphere, and the distribution of radial linear statistics of the 2dOCP in the plane