The Drosophila pericentrin-like protein is essential for cilia/flagella function, but appears to be dispensable for mitosis

Centrosomes consist of a pair of centrioles surrounded by an amorphous pericentriolar material (PCM). Proteins that contain a Pericentrin/AKAP450 centrosomal targeting (PACT) domain have been implicated in recruiting several proteins to the PCM. We show that the only PACT domain protein in Drosophila (the Drosophila pericentrin-like protein [D-PLP]) is associated with both the centrioles and the PCM, and is essential for the efficient centrosomal recruitment of all six PCM components that we tested. Surprisingly, however, all six PCM components are eventually recruited to centrosomes during mitosis in d-plp mutant cells, and mitosis is not dramatically perturbed. Although viable, d-plp mutant flies are severely uncoordinated, a phenotype usually associated with defects in mechanosensory neuron function. We show that the sensory cilia of these neurons are malformed and the neurons are nonfunctional in d-plp mutants. Moreover, the flagella in mutant sperm are nonmotile. Thus, D-PLP is essential for the formation of functional cilia and flagella in flies

The Humanities and the Public Soul 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73120/1/j.1467-8330.2008.00615.x.pd

Development of High Resolution Scintillator Systems Based on Photocell Technology

Inorganic scintillator/photomultiplier-based spectrometers are the systems of choice for a multitude of X-ray and gamma radiation measurement applications. Despite widespread use, they have numerous shortcomings. The most serious shortcoming is the relatively poor energy resolution that makes isotope identification problematic, particularly in the case of trace quantities. Energy resolution in scintillator/photomultiplier tube (PMT) spectrometers is governed by a combination of the crystal intrinsic resolution that includes non-linearity effects, photomultiplier statistics, and the variability in the probability of a scintillation photon generating a photoelectron at the photocathode. It is evident that energy resolution in these systems is linked to both the physics of light generation in the scintillator and the characteristics of the PMT. PMTs also present design problems, especially in the case of handheld and portable instruments, due to their considerable weight and volume. Additionally, PMTs require well-regulated high voltage, and are vulnerable to magnetic fields. The objective of this work is to provide instrument designers of scintillation-based gamma-ray spectrometers with superior energy resolution and greatly reduced weight and volume. It is planned to achieve this advancement by optimizing the performance of a new class of inorganic scintillators by matching their emission spectra with the enhanced quantum efficiency of certain photocells

The Age Of Globular Clusters In Light Of Hipparcos: Resolving the Age Problem?

We review five independent techniques which are used to set the distance scale to globular clusters, including subdwarf main sequence fitting utilizing the recent Hipparcos parallax catalogue. These data together all indicate that globular clusters are farther away than previously believed, implying a reduction in age estimates. This new distance scale estimate is combined with a detailed numerical Monte Carlo study designed to assess the uncertainty associated with the theoretical age-turnoff luminosity relationship in order to estimate both the absolute age and uncertainty in age of the oldest globular clusters. Our best estimate for the mean age of the oldest globular clusters is now $11.5\pm 1.3$Gyr, with a one-sided, 95% confidence level lower limit of 9.5 Gyr. This represents a systematic shift of over 2 $\sigma$ compared to our earlier estimate, due completely to the new distance scale---which we emphasize is not just due to the Hipparcos data. This now provides a lower limit on the age of the universe which is consistent with either an open universe, or a flat, matter dominated universe (the latter requiring H_0 \le 67 \kmsmpc). Our new study also explicitly quantifies how remaining uncertainties in the distance scale and stellar evolution models translate into uncertainties in the derived globular cluster ages. Simple formulae are provided which can be used to update our age estimate as improved determinations for various quantities become available.Comment: 41 pages, including 10 eps figs, uses aaspp4.sty and flushrt.sty, submitted to Ap.J., revised to incorporate FULL Hipparcos catalogue dat

The Insulin Resistance Intervention after Stroke trial: a perspective on future practice and research

The prevention of recurrent events after ischaemic stroke and transient ischaemic attack is well established and based on lifestyle changes, antithrombotics, statins, antihypertensives and carotid surgery. The international IRIS trial assessed whether pioglitazone, a glucose-lowering insulin-sensitizing drug, would reduce recurrent vascular events in patients with ischaemic stroke or transient ischaemic attack. After 4.8 years, pioglitazone therapy was associated with reduced vascular events and new diabetes, and an increase in weight, oedema and bone fractures. Pioglitazone may add to the strategies for preventing further events in patients with stroke or transient ischaemic attack

Testing The Friedmann Equation: The Expansion of the Universe During Big-Bang Nucleosynthesis

In conventional general relativity, the expansion rate H of a Robertson-Walker universe is related to the energy density by the Friedmann equation. Aside from the present day, the only epoch at which we can constrain the expansion history in a model-independent way is during Big-Bang Nucleosynthesis (BBN). We consider a simple two-parameter characterization of the behavior of H during BBN and derive constraints on this parameter space, finding that the allowed region of parameter space is essentially one-dimensional. We also study the effects of a large neutrino asymmetry within this framework. Our results provide a simple way to compare an alternative cosmology to the observational requirement of matching the primordial abundances of the light elements.Comment: 18 pages, Final version to be published in Phys. Rev.

Big Bang Nucleosynthesis Constraints on Primordial Magnetic Fields

We reanalyze the effect of magnetic fields in BBN, incorporating several features which were omitted in previous analyses. We find that the effects of coherent magnetic fields on the weak interaction rates and the electron thermodynamic functions (\rhoe, \Pe, and \drhoedt ) are unimportant in comparison to the contribution of the magnetic field energy density in BBN. In consequence the effect of including magnetic fields in BBN is well approximated numerically by treating the additional energy density as effective neutrino number. A conservative upper bound on the primordial magnetic field, parameterized as $\zeta=2eB_{rms}/(T_\nu^2)$, is $\zeta \le 2$ ($\rho_B < 0.27 \rho_\nu$). This bound can be stronger than the conventional bound coming from the Faraday rotation measures of distant quasars if the cosmological magnetic field is generated by a causal mechanism.Comment: Latex, 20 pages, 3 uuencoded figures appende

Drosophila TRPN( = NOMPC) Channel Localizes to the Distal End of Mechanosensory Cilia

BACKGROUND: A TRPN channel protein is essential for sensory transduction in insect mechanosensory neurons and in vertebrate hair cells. The Drosophila TRPN homolog, NOMPC, is required to generate mechanoreceptor potentials and currents in tactile bristles. NOMPC is also required, together with a TRPV channel, for transduction by chordotonal neurons of the fly's antennal ear, but the TRPN or TRPV channels have distinct roles in transduction and in regulating active antennal mechanics. The evidence suggests that NOMPC is a primary mechanotransducer channel, but its subcellular location-key for understanding its exact role in transduction-has not yet been established. METHODOLOGY/PRINCIPAL FINDINGS: Here, by immunostaining, we locate NOMPC at the tips of mechanosensory cilia in both external and chordotonal sensory neurons, as predicted for a mechanotransducer channel. In chordotonal neurons, the TRPN and TRPV channels are respectively segregated into distal and proximal ciliary zones. This zonal separation is demarcated by and requires the ciliary dilation, an intraciliary assembly of intraflagellar transport (IFT) proteins. CONCLUSIONS: Our results provide a strong evidence for NOMPC as a primary transduction channel in Drosophila mechansensory organs. The data also reveals a structural basis for the model of auditory chordotonal transduction in which the TRPN and TRPV channels play sequential roles in generating and amplifying the receptor potential, but have opposing roles in regulating active ciliary motility