Constrained Multilevel Latent Class Models for the Analysis of Three-Way Three-Mode Binary Data

Probabilistic feature models (PFMs) can be used to explain binary rater judgements about the associations between two types of elements (e.g., objects and attributes) on the basis of binary latent features. In particular, to explain observed object-attribute associations PFMs assume that respondents classify both objects and attributes with respect to a, usually small, number of binary latent features, and that the observed object-attribute association is derived as a specific mapping of these classifications. Standard PFMs assume that the object-attribute association probability is the same according to all respondents, and that all observations are statistically independent. As both assumptions may be unrealistic, a multilevel latent class extension of PFMs is proposed which allows objects and/or attribute parameters to be different across latent rater classes, and which allows to model dependencies between associations with a common object (attribute) by assuming that the link between features and objects (attributes) is fixed across judgements. Formal relationships with existing multilevel latent class models for binary three-way data are described. As an illustration, the models are used to study rater differences in product perception and to investigate individual differences in the situational determinants of anger-related behavior.     

Radiation embryology

Summary Prenatal development, characterized by intensive cell proliferation, cell differentiation and cell migration, shows a high radiosensitivity. Therefore, radiation exposure of embryos and fetuses is of great concern for radiological protection and human health. Irradiation during gestation can cause death, growth disorders, malformations, functional impairment and malignant diseases in childhood. These effects are strongly dependent on the developmental stage at exposure and on the radiation dose. The first trimester of pregnancy is regarded as the period with the highest risk for malformation and cancer induction. The developing nervous system shows a special susceptibility to ionizing radiation over a long period and is therefore of great significance for risk estimation. Knowledge about radiation effects on prenatal development has been derived from animal experimentation and from the exposure of human embryos. There is evidence that doses between 1 and 10 cGy may lead to developmental anomalies and that the radiation response can be modified by additional factors.     

Teratogenic interactions between cadmium and radiation in mice

Summary Mouse embryos were exposed to various doses of cadmium and/or X-rays on day 8 of gestation. The combined treatment exerted an antagonistic effect regarding the teratogenic action of the two agents.     

Ergastoplasmic granules,cytophysiological adaptation of the locusts corpora cardiaca to migratory flights?

Summary A good correlation was shown between the presence of ergastoplasmic granules in the glandular cells of the locusts corpora cardiaca and the flight activity of these insects.Research supported by grants A.T.P. No. 1831 and E.R.A. No. 620 from the Centre National de la Recherche Scientifique, French Ministry.     

Binding of 3,3',5'-triiodo-L-thyronine (rT3) to human serum proteins]

The rT3-binding and human serum proteins was directly studied with tracer doses of radioactive rT3. Polyacrylamide gel electrophoresis showed 125I-rT3 added to human serum was distributed among two proteins: albumin (carrying 57% of tracer rT3) and TBPA )22%). No binding was observed to TBG, protein binding T4.     

Functional coordination of intraflagellar transport motors

Cilia have diverse roles in motility and sensory reception, and defects in cilia function contribute to ciliary diseases such as Bardet-Biedl syndrome (BBS). Intraflagellar transport (IFT) motors assemble and maintain cilia by transporting ciliary precursors, bound to protein complexes called IFT particles, from the base of the cilium to their site of incorporation at the distal tip. In Caenorhabditis elegans, this is accomplished by two IFT motors, kinesin-II and osmotic avoidance defective (OSM)-3 kinesin, which cooperate to form two sequential anterograde IFT pathways that build distinct parts of cilia. By observing the movement of fluorescent IFT motors and IFT particles along the cilia of numerous ciliary mutants, we identified three genes whose protein products mediate the functional coordination of these motors. The BBS proteins BBS-7 and BBS-8 are required to stabilize complexes of IFT particles containing both of the IFT motors, because IFT particles in bbs-7 and bbs-8 mutants break down into two subcomplexes, IFT-A and IFT-B, which are moved separately by kinesin-II and OSM-3 kinesin, respectively. A conserved ciliary protein, DYF-1, is specifically required for OSM-3 kinesin to dock onto and move IFT particles, because OSM-3 kinesin is inactive and intact IFT particles are moved by kinesin-II alone in dyf-1 mutants. These findings implicate BBS ciliary disease proteins and an OSM-3 kinesin activator in the formation of two IFT pathways that build functional cilia.     

Disruption of Bardet-Biedl syndrome ciliary proteins perturbs planar cell polarity in vertebrates

The evolutionarily conserved planar cell polarity (PCP) pathway (or noncanonical Wnt pathway) drives several important cellular processes, including epithelial cell polarization, cell migration and mitotic spindle orientation. In vertebrates, PCP genes have a vital role in polarized convergent extension movements during gastrulation and neurulation. Here we show that mice with mutations in genes involved in Bardet-Biedl syndrome (BBS), a disorder associated with ciliary dysfunction, share phenotypes with PCP mutants including open eyelids, neural tube defects and disrupted cochlear stereociliary bundles. Furthermore, we identify genetic interactions between BBS genes and a PCP gene in both mouse (Ltap, also called Vangl2) and zebrafish (vangl2). In zebrafish, the augmented phenotype results from enhanced defective convergent extension movements. We also show that Vangl2 localizes to the basal body and axoneme of ciliated cells, a pattern reminiscent of that of the BBS proteins. These data suggest that cilia are intrinsically involved in PCP processes.