Prolactin and growth hormone do not interfere with the response of mouse testes to hCG in vitro

Summary In incubations of decapsulated mouse testes with a maximally stimulating dose of hCG, the accumulation of testosterone was not affected by the addition of PRL at concentrations from 0.1 to 50 μg/ml or GH at concentrations from 0.5 to 25 μg/ml. This work was supported by NIH through grants HD 12642 and HD 12671. We thank NIAMDD for the supply of pituitary hormones and Dr B.V. Caldwell for antiserum to testosterone.     

Genetic variegation of clonal architecture and propagating cells in leukaemia

Little is known of the genetic architecture of cancer at the subclonal and single-cell level or in the cells responsible for cancer clone maintenance and propagation. Here we have examined this issue in childhood acute lymphoblastic leukaemia in which the ETV6-RUNX1 gene fusion is an early or initiating genetic lesion followed by a modest number of recurrent or 'driver' copy number alterations. By multiplexing fluorescence in situ hybridization probes for these mutations, up to eight genetic abnormalities can be detected in single cells, a genetic signature of subclones identified and a composite picture of subclonal architecture and putative ancestral trees assembled. Subclones in acute lymphoblastic leukaemia have variegated genetics and complex, nonlinear or branching evolutionary histories. Copy number alterations are independently and reiteratively acquired in subclones of individual patients, and in no preferential order. Clonal architecture is dynamic and is subject to change in the lead-up to a diagnosis and in relapse. Leukaemia propagating cells, assayed by serial transplantation in NOD/SCID IL2Rγ(null) mice, are also genetically variegated, mirroring subclonal patterns, and vary in competitive regenerative capacity in vivo. These data have implications for cancer genomics and for the targeted therapy of cancer.     

Aspartate 112 is the selectivity filter of the human voltage-gated proton channel

The ion selectivity of pumps and channels is central to their ability to perform a multitude of functions. Here we investigate the mechanism of the extraordinary selectivity of the human voltage-gated proton channel, H(V)1 (also known as HVCN1). This selectivity is essential to its ability to regulate reactive oxygen species production by leukocytes, histamine secretion by basophils, sperm capacitation, and airway pH. The most selective ion channel known, H(V)1 shows no detectable permeability to other ions. Opposing classes of selectivity mechanisms postulate that (1) a titratable amino acid residue in the permeation pathway imparts proton selectivity, or (2) water molecules 'frozen' in a narrow pore conduct protons while excluding other ions. Here we identify aspartate 112 as a crucial component of the selectivity filter of H(V)1. When a neutral amino acid replaced Asp?112, the mutant channel lost proton specificity and became anion-selective or did not conduct. Only the glutamate mutant remained proton-specific. Mutation of the nearby Asp?185 did not impair proton selectivity, indicating that Asp?112 has a unique role. Although histidine shuttles protons in other proteins, when histidine or lysine replaced Asp?112, the mutant channel was still anion-permeable. Evidently, the proton specificity of H(V)1 requires an acidic group at the selectivity filter.     

Seismic considerations for spent nuclear fuel storage in dry casks

o aid the United States’ Nuclear Regulatory Commission, Sandia National Laboratories (SNL) was contracted to investigate the seismic behavior of typical dry cask storage systems. Parametric evaluations characterized the sensitivity of calculated cask response characteristics to input parameters. The parametric evaluation investigated two generic cask design (cylindrical and rectangular), three different foundation types (soft soil, hard soil, and rock), and three different cask to pad coefficients of friction (0.2, 0.55, 0.8) for earthquakes with peak ground accelerations of 0.25g, 0.6g, 1.0g and 1.25g. A total of 1 165 analyses were completed, with regression analyses being performed on the resulting cask response data to determine relationships relating the mean (and 16 % and 84 % confidence intervals on the mean) to peak ground acceleration, peak ground velocity, and pseudo-spectral acceleration at 1 Hz and 5 % damping. In general, the cylindrical casks experienced significantly larger responses in comparison to the rectangular cask. The cylindrical cask experienced larger top of cask displacements, larger cask rotations (rocking), and more occurrences of cask toppling (the rectangular cask never toppled over). The cylindrical cask was also susceptible to rolling once rocking had been initiated, a behavior not observed in the rectangular cask. Cask response was not overly sensitive to foundation type, but was significantly dependent on the response spectrum employed.     

Suppression of star formation in early-type galaxies by feedback from supermassive black holes

Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.     

Boc is a receptor for sonic hedgehog in the guidance of commissural axons

In the spinal cord, sonic hedgehog (Shh) is secreted by the floor plate to control the generation of distinct classes of ventral neurons along the dorsoventral axis. Genetic and in vitro studies have shown that Shh also later acts as a midline-derived chemoattractant for commissural axons. However, the receptor(s) responsible for Shh attraction remain unknown. Here we show that two Robo-related proteins, Boc and Cdon, bind specifically to Shh and are therefore candidate receptors for the action of Shh as an axon guidance ligand. Boc is expressed by commissural neurons, and targeted disruption of Boc in mouse results in the misguidance of commissural axons towards the floor plate. RNA-interference-mediated knockdown of Boc impairs the ability of rat commissural axons to turn towards an ectopic source of Shh in vitro. Taken together, these data suggest that Boc is essential as a receptor for Shh in commissural axon guidance.     

Direct ink writing of polycaprolactone/polyethylene oxide based 3D constructs

There has been increasing interest over recent years in the application of three-dimensional(3 D) printing technologies in the biomedical field. One such method is Direct Ink Writing(DIW); this approach has the potential advantage of allowing room-temperature deposition of materials, presented as an ink, to build complex architectures. DIW offers the ability to process biomaterials containing temperature-sensitive components. Due to the fabrication principles of DIW, there are specific rheologic...