3D collagen type I matrix inhibits the antimigratory effect of doxorubicin

Background  

The cell microenvironment, especially extracellular matrix proteins, plays an important role in tumor cell response to chemotherapeutic drugs. The present study was designed to investigate whether this microenvironment can influence the antimigratory effect of an anthracycline drug, doxorubicin, when tumor cells are grown in a matrix of type I collagen, a three-dimensional (3D) context which simulates a natural microenvironment.     

On the empirical choice of the time window for restricted mean survival time

The t-year mean survival or restricted mean survival time (RMST) has been used as an appealing summary of the survival distribution within a time window [0, t]. RMST is the patient's life expectancy until time t and can be estimated nonparametrically by the area under the Kaplan-Meier curve up to t. In a comparative study, the difference or ratio of two RMSTs has been utilized to quantify the between-group-difference as a clinically interpretable alternative summary to the hazard ratio. The choice of the time window [0, t] may be prespecified at the design stage of the study based on clinical considerations. On the other hand, after the survival data have been collected, the choice of time point t could be data-dependent. The standard inferential procedures for the corresponding RMST, which is also data-dependent, ignore this subtle yet important issue. In this paper, we clarify how to make inference about a random “parameter.” Moreover, we demonstrate that under a rather mild condition on the censoring distribution, one can make inference about the RMST up to t, where t is less than or even equal to the largest follow-up time (either observed or censored) in the study. This finding reduces the subjectivity of the choice of t empirically. The proposal is illustrated with the survival data from a primary biliary cirrhosis study, and its finite sample properties are investigated via an extensive simulation study.     

Cladistic analysis of Aradidae (Insecta,Heteroptera) based on morphological and molecular characters

In this study, we present for the first time a cladistic analysis of the subfamilies of Aradidae, using molecular and morphological characters. Eighty‐three taxa, including 79 species representing eight subfamilies, are treated. The analyses were performed using 72 morphological characters and approximately 1650 bp corresponding to three molecular loci (CO1, 16S and 28S). Characters were analysed using parsimony and Bayesian methods. Based on the combined analyses, we find support for the monophyly of Aradidae, including the subfamilies Aradinae, Aneurinae, Calisiinae, Isoderminae, and Mezirinae and the paraphyly of Prosympiestinae and Chinamyersiinae. In all analyses, Prosympiestinae includes Isoderminae. The Termitaphididae were not found sister to the Aradidae in the Aradoidea.     

Phylogenetic algorithms and the evolution of species communities in forest fragments

In forest fragmentation studies, low specific richness in small fragments and community nestedness are usually considered to result from species loss. However, except in the case of fragmentation experiments, these studies cannot distinguish between original low richness and secondary species loss, or between original high richness and secondary colonizations in fragments. To distinguish between these possibilities is a matter of historical inference for which phylogenetic algorithms are designed. The methods of phylogenetic analysis, and especially parsimony analysis, can be used to find a tree of relationships between communities from different forest fragments, taking the presence or absence of species among different communities as characters. Parsimony analysis searches if species subsets can be classified in a nested hierarchy, and also establishes how the communities evolved, polarizing species changes into either extinctions or colonizations. By re‐analyzing two classical studies in this new and powerful way, we demonstrate that the differences between fragments and large continuous forests cannot be attributed to species loss in all cases, contrary to expectations from models. © The Willi Hennig Society 2005.