A multiple comparison procedure for dose-finding trials with subpopulations

Identifying subgroups of patients with an enhanced response to a new treatment has become an area of increased interest in the last few years. When there is knowledge about possible subpopulations with an enhanced treatment effect before the start of a trial it might be beneficial to set up a testing strategy, which tests for a significant treatment effect not only in the full population, but also in these prespecified subpopulations. In this paper, we present a parametric multiple testing approach for tests in multiple populations for dose-finding trials. Our approach is based on the MCP-Mod methodology, which uses multiple comparison procedures (MCPs) to test for a dose–response signal, while considering multiple possible candidate dose–response shapes. Our proposed methods allow for heteroscedastic error variances between populations and control the family-wise error rate over tests in multiple populations and for multiple candidate models. We show in simulations that the proposed multipopulation testing approaches can increase the power to detect a significant dose–response signal over the standard single-population MCP-Mod, when the specified subpopulation has an enhanced treatment effect.     

Demography,dispersal and movement pattern of <Emphasis Type="Italic">Euphydryas aurinia</Emphasis> (Lepidoptera: Nymphalidae) at the Iberian Peninsula: an alarming example in an increasingly fragmented landscape?

Mediterranean countries like Portugal and Spain, so far characterised by extensive traditional land use over major parts of their territories, have been less affected by species losses. However, they are facing severe changes. As a model organism we chose the butterfly Euphydryas aurinia, highly threatened in Central Europe but still common at the Iberian Peninsula, for a mark-release-recapture survey in the western Algarve. We examined key factors for stabile metapopulation systems to assess the ability of long-term survival in the increasingly fragmented landscapes of the Iberian Peninsula. The density of the examined population was high (ca. 2,200 individuals/ha). However, the MRR-based proportion of individuals moving longer distance classes showed a better fit to the negative exponential function than to the inverse power function implying restricted dispersal behaviour. The orientation pattern of short distance movements (<10 m) proved to be independent from habitat structures. In contrast, longer movements (>10 m) were strongly orientated along the main habitat axes revealing the importance of internal habitat structures for the orientation of dispersing individuals. Based on these data, we discuss the severe consequences for the fauna of the Iberian Peninsula in an increasingly fragmented and monotonous landscape.     

N-Hydroxyguanidines oxidation by a N3S copper-complex mimicking the reactivity of Dopamine β-Hydroxylase

N-Aryl-N′-hydroxyguanidines are compounds that display interesting pharmacological properties but their chemical reactivity remains poorly investigated. Some of these compounds are substrates for the heme-containing enzymes nitric-oxide synthases (NOS) and act as reducing co-substrates for the copper-containing enzyme Dopamine β-Hydroxylase (DBH) [P. Slama, J.L. Boucher, M. Réglier, Biochem. Biophys. Res. Commun. 316 (2004) 1081-1087]. DBH catalyses the hydroxylation of the important neurotransmitter dopamine into norepinephrine in the presence of both molecular oxygen and a reducing co-substrate. Although many molecules have been used as co-substrates for DBH, their interaction at the active site of DBH and their role in mechanism are not clearly characterized. In the present paper, we have used a water-soluble copper-N₃S complex that mimics the Cu_B site of DBH, and aromatic N-hydroxyguanidines as reducers to address this question. N-Aryl-N′-hydroxyguanidines readily reduced copper(II) to Cu(I) and were oxidized into a nitrosoamidine as previously observed in reactions performed with purified DBH. These data describe for the first time the reactivity of N-aryl-N′-hydroxyguanidines with a water-soluble copper(II) complex and help to understand the interaction of co-substrates with copper at the active site of DBH.     

Pitchfork and Gprasp2 Target Smoothened to the Primary Cilium for Hedgehog Pathway Activation

The seven-transmembrane receptor Smoothened (Smo) activates all Hedgehog (Hh) signaling by translocation into the primary cilia (PC), but how this is regulated is not well understood. Here we show that Pitchfork (Pifo) and the G protein-coupled receptor associated sorting protein 2 (Gprasp2) are essential components of an Hh induced ciliary targeting complex able to regulate Smo translocation to the PC. Depletion of Pifo or Gprasp2 leads to failure of Smo translocation to the PC and lack of Hh target gene activation. Together, our results identify a novel protein complex that is regulated by Hh signaling and required for Smo ciliary trafficking and Hh pathway activation.     

Incomplete proteasomal degradation of green fluorescent proteins in the context of tandem fluorescent protein timers

Tandem fluorescent protein timers (tFTs) report on protein age through time-dependent change in color, which can be exploited to study protein turnover and trafficking. Each tFT, composed of two fluorescent proteins (FPs) that differ in maturation kinetics, is suited to follow protein dynamics within a specific time range determined by the maturation rates of both FPs. So far, tFTs have been constructed by combining slower-maturing red fluorescent proteins (redFPs) with the faster-maturing superfolder green fluorescent protein (sfGFP). Toward a comprehensive characterization of tFTs, we compare here tFTs composed of different faster-maturing green fluorescent proteins (greenFPs) while keeping the slower-maturing redFP constant (mCherry). Our results indicate that the greenFP maturation kinetics influences the time range of a tFT. Moreover, we observe that commonly used greenFPs can partially withstand proteasomal degradation due to the stability of the FP fold, which results in accumulation of tFT fragments in the cell. Depending on the order of FPs in the timer, incomplete proteasomal degradation either shifts the time range of the tFT toward slower time scales or precludes its use for measurements of protein turnover. We identify greenFPs that are efficiently degraded by the proteasome and provide simple guidelines for the design of new tFTs.     

Estimation of Box's ε for low‐ and high‐dimensional repeated measures designs with unequal covariance matrices

We present new inference methods for the analysis of low‐ and high‐dimensional repeated measures data from two‐sample designs that may be unbalanced, the number of repeated measures per subject may be larger than the number of subjects, covariance matrices are not assumed to be spherical, and they can differ between the two samples. In comparison, we demonstrate how crucial it is for the popular Huynh‐Feldt (HF) method to make the restrictive and often unrealistic or unjustifiable assumption of equal covariance matrices. The new method is shown to maintain desired α‐levels better than the well‐known HF correction, as demonstrated in several simulation studies. The proposed test gains power when the number of repeated measures is increased in a manner that is consistent with the alternative. Thus, even increasing the number of measurements on the same subject may lead to an increase in power. Application of the new method is illustrated in detail, using two different real data sets. In one of them, the number of repeated measures per subject is smaller than the sample size, while in the other one, it is larger.