Premature Sister Chromatid Separation Is Poorly Detected by the Spindle Assembly Checkpoint as a Result of System-Level Feedback

Sister chromatid cohesion, mediated by the cohesin complex, is essential for faithful mitosis. Nevertheless, evidence suggests that the surveillance mechanism that governs mitotic fidelity, the spindle assembly checkpoint (SAC), is not robust enough to halt cell division when cohesion loss occurs prematurely. The mechanism behind this poor response is not properly understood. Using developing Drosophila brains, we show that full sister chromatid separation elicits a weak checkpoint response resulting in abnormal mitotic exit after a short delay. Quantitative live-cell imaging approaches combined with mathematical modeling indicate that weak SAC activation upon cohesion loss is caused by weak signal generation. This is further attenuated by several feedback loops in the mitotic signaling network. We propose that multiple feedback loops involving cyclin-dependent kinase 1 (Cdk1) gradually impair error-correction efficiency and accelerate mitotic exit upon premature loss of cohesion. Our findings explain how cohesion defects may escape SAC surveillance.

Biosystematics of the Genus Andryala L. (Asteraceae)

Andryala (Asteraceae: Cichorieae) is a little-known Mediterranean-Macaronesian genus whose taxonomy is much in need of revision. The aim of the present biosystematic study was to elucidate species relationships within this genus based on morphological and molecular data. In this study several taxa are recognised: 17 species, 14 subspecies, and 3 hybrids. Among these, 5 species are Macaronesian endemics (A. glandulosa, A. sparsiflora, A. crithmifolia Aiton, A. pinnatifida, and A. perezii), 4 species are Northwest African endemics (A. mogadorensis, A. maroccana, A. chevallieri, and A. nigricans) and one species is endemic to Romania (A. laevitomentosa). Historical background regarding taxonomic delimitation in the genus is addressed from Linnaean to present day concepts, as well as the origin of the name Andryala. The origin of Asteraceae and the systematic position of Andryala is shortly summarised. The morphological study was based on a bibliographic review and the revision of 1066 specimens of 13 herbaria as well as additional material collected during fieldwork. The variability of the morphological characters of the genus, including both vegetative taxonomic characters (root, stem, leaf and indumentum characters) and reproductive ones (inflorescence, floret, fruit and pappus characters), is assessed. Numerical analysis of the morphological data was performed using different similarity or dissimilarity measures and coefficients, as well as ordination and clustering methods. Results support the segregation of the recognised taxa and the congruence of the several analyses in the separation of the recognised taxa (using quantitative, binary or multi-state characters). The proposed taxonomy for Andryala includes a new infra-generic classification, new taxa and new combinations and ranks, typifications and diagnostic keys (one for the species and several for subspecies). For each taxon a list of synonyms, typification comments and a detailed description are provided, just as comments on taxonomy and nomenclature, and a brief discussion on karyology. Additionally, information on ecology and conservation status as well as on distribution and a list of studied material are also presented. Phylogenetic analyses based on different nuclear and chloroplast DNA markers, using Bayesian and maximum parsimony methods of inference, were performed. Results support three main lineages: separate ones for the relict species A. agardhii and A. laevitomentosa and a third including the majority of the Andryala species that underwent a relatively rapid and recent speciation. They also suggest a single colonization event of Madeira and the Canary Islands from the Mediterranean region, followed by insular speciation. Biogeography and speciation within the genus are briefly discussed, including a proposal for the centre of origin of the genus and possible dispersal routes.

FAIRLIE: Stata module to generate nonlinear decomposition of binary outcome differentials

fairlie computes the nonlinear decomposition of binary outcome differentials proposed by Fairlie (1999, 2003).

Maternal separation followed by isolation-housing differentially affects prepulse inhibition of the acoustic startle response in C57BL/6 mice

Exposure to chronic stress is associated with an increased incidence of neuropsychiatric dysfunction. The current study evaluated two competing hypotheses, the cumulative stress and the match/mismatch hypothesis of neuropsychiatric dysfunction, using two paradigms relating to exposure to “stress”: pre-weaning maternal separation and post-weaning isolation-housing. C57BL/6 offspring were reared under four conditions: typical animal facility rearing (AFR, control), early handling (EH, daily 15 min separation from dam), maternal separation (MS, daily 4 hr separation from dam), and maternal and peer separation (MPS, daily 4 hr separation from dam and from littermates). After weaning, mice were either housed socially (2–3/cage) or in isolation (1/cage) and then tested for prepulse inhibition in adulthood. Isolation-housed MPS subjects displayed greater deficits in prepulse inhibition relative to socially-housed MPS subjects while socially-housed AFR subjects displayed greater deficits in prepulse inhibition relative to isolation-housed AFR subjects. The results indicate that these treatment conditions represent a potentially valuable model for evaluating the match/mismatch hypothesis in regards to neuropsychiatric dysfunction.

Treatment of combined sewer overflows by high gradient magnetic separation : on-site testing with mobile pilot plant trailer /

Mode of access: Internet.

Source separation collection and processing equipment : final report.

"January 1981"--Cover.

Source separation : the community awareness program in Somerville and Marblehead, Massachusetts /

Mode of access: Internet.

Magnetic separation : recovery of saleable iron and steel from municipal solid waste /

Mode of access: Internet.

Study of activated sludge separation by dynamic straining /

Mode of access: Internet.

Oil/water separation : state-of-the-art /

Mode of access: Internet.

Isotope separation by gaseous diffusion and centrifugation : a literature search /

"Stable Isotope Separation."

Upon whom rests the guilt of the war? Separation: war without end.

Caption title: Disunion: degradation without remedy.

Investigation of driver reactions to tread separation scenarios in the National Advanced Driving Simulator (NADS).

Decreasing vehicle understeer was strongly associated with the likelihood of control loss following both the unexpected and expected tire failures. Knowledge of the imminent tread separation reduced the overall probability of control loss from 55% to 20% and had a significant effect on how quickly drivers responded as well as on the nature of their initial responses (i.e., steering orbraking). Driver age was marginally associated with increased likelihood of vehicle control loss, but only on unexpected trials. Vehicle speed at the time of first steering input also contributed to the probability of control loss. Neither the location of the tire that failed (left rear vs. right rear) nor the specific instructions about how best to respond to the tread separation influenced the probability of control loss. Differences associated with vehicle understeer conditions observed in the present study were large and consistent, independent of driver expectations and across driver age groups. It is thus fair to conclude that in the event of a complete rear-tire detread, the increased difficulty in vehicle handling and the associated increased likelihood of loss of vehicle control with decreasing vehicle understeer generalize to real-world driving.

Experiment in assessing color separation techniques for identifying small density variations in tires. Interim report.

National Highway Traffic Safety Administration, Research Institute, Washington, D.C.

On a tabulation of reduced binary quadratic forms of a negative determinant,

The author's thesis (Ph.D.)--University of California, 1913.