ESCRT function in cytokinesis: location, dynamics and regulation by mitotic kinases

Mammalian cytokinesis proceeds by constriction of an actomyosin ring and furrow ingression, resulting in the formation of the midbody bridge connecting two daughter cells. At the centre of the midbody resides the Flemming body, a dense proteinaceous ring surrounding the interlocking ends of anti-parallel microtubule arrays. Abscission, the terminal step of cytokinesis, occurs near the Flemming body. A series of broad processes govern abscission: the initiation and stabilisation of the abscission zone, followed by microtubule severing and membrane scission—The latter mediated by the endosomal sorting complex required for transport (ESCRT) proteins. A key goal of cell and developmental biologists is to develop a clear understanding of the mechanisms that underpin abscission, and how the spatiotemporal coordination of these events with previous stages in cell division is accomplished. This article will focus on the function and dynamics of the ESCRT proteins in abscission and will review recent work, which has begun to explore how these complex protein assemblies are regulated by the cell cycle machinery

North Dakota Student Teacher Performance Based on the Intasc Model Standards and the Qualifications of Cooperating Teachers

Demand for improving public schools and teacher preparation programs at institutions of higher education has precipitated a standards-setting movement in the United States in which schools, teachers, and teacher preparation programs are and will continue to be held accountable for meeting standards. This is a time in our educational history in which teachers are being forced to meet certain standards and criteria based on competency in their subject area and in educational pedagogy. With the passage of No Child Left Behind, teachers at all levels will be held accountable to meet new guidelines and standards. The purpose of this study was to analyze cooperating teachers’ ratings of the performance of student teachers graduating from North Dakota teacher preparation programs based on the INTASC (Interstate New Teacher Assessment and Support Consortium) model standards for beginning teachers and to determine if the cooperating teachers’ years of teaching experience, level of education, and total number of student teachers the cooperating teacher has had in his/her teaching career were predictors of the ratings. The INTASC principles include knowledge of subject, learning and human development, adapting instruction, strategies, motivation and management, communication skills, planning, assessment, commitment, and partnership. After the data (n = 103) were collected from an online survey entitled the North Dakota Student Teaching Survey, descriptive statistics based on each INTASC principle were displayed. The highest mean score was in the area of professional commitment and responsibility, and the lowest mean score was in the area of classroom motivation and management. Standard statistical methodologies were used to report if student teacher ratings were related to a cooperating teacher’s specific qualifications as implemented in this study. The performance rating of student teachers was indicated via selecting one response on a four-point Likert Scale. The respondents’ choices included the following criteria: 4 = Exceptional; 3 = Strong; 2 = Adequate; and 1 = Needs Improvement. Results indicated teacher experience to be a consistently significant predictor of the student teachers’ rating on the North Dakota Student Teaching Survey for the INTASC principles of knowledge of subject, learning and human development, adapting instruction, strategies, motivation and management, planning, assessment, commitment, and partnership. When combined with teaching experience, the number of student teachers a cooperating teacher had during his/her career also predicted the rating of student teachers for INTASC principles of knowledge of subject, strategies, and planning. Educational level was found to be a significant predictor of the student teachers’ ratings only for the INTASC principle of assessment. INTASC principle of communication skills was not a predictor of the student teachers’ rating

A complex network of interactions between mitotic kinases, phosphatases and ESCRT proteins regulates septation and membrane trafficking in S. pombe

Cytokinesis and cell separation are critical events in the cell cycle. We show that Endosomal Sorting Complex Required for Transport (ESCRT) genes are required for cell separation in Schizosaccharomyces pombe. We identify genetic interactions between ESCRT proteins and polo and aurora kinases and Cdc14 phosphatase that manifest as impaired growth and exacerbated defects in septation, suggesting that the encoded proteins function together to control these processes. Furthermore, we observed defective endosomal sorting in mutants of plo1, ark1 and clp1, as has been reported for ESCRT mutants, consistent with a role for these kinases in the control of ESCRT function in membrane traffic. Multiple observations indicate functional interplay between polo and ESCRT components: firstly, two-hybrid in vivo interactions are reported between Plo1p and Sst4p, Vps28p, Vps25p, Vps20p and Vps32p; secondly, co-immunoprecipitation of human homologues of Vps20p, Vps32p, Vps24p and Vps2p by human Plk1; and thirdly, in vitro phosphorylation of budding yeast Vps32p and Vps20p by polo kinase. Two-hybrid analyses also identified interactions between Ark1p and Vps20p and Vps32p, and Clp1p and Vps28p. These experiments indicate a network of interactions between ESCRT proteins, plo1, ark1 and clp1 that coordinate membrane trafficking and cell separation in fission yeast

DEKAS - An evolutionary case-based reasoning system to support protection scheme design

This paper describes a decision support system being developed in conjunction with two UK utility companies to aid the design of electrical power transmission protection systems. A brief overview of the application domain is provided, followed by a description of the work carried out to date concerning the development and deployment of the Design Engineering Knowledge Application System (DEKAS). The paper then discusses the provision of intelligent decision support to the design engineer through the application of case-based reasoning (CBR). The key benefits from this will be outlined in conjunction with a relevant case study

The Stellar Mass Evolution of Galaxies in the NICMOS Ultra Deep Field

We measure the build-up of the stellar mass of galaxies from z=6 to z=1. Using 15 band multicolor imaging data in the NICMOS Ultra Deep Field we derive photometric redshifts and masses for 796 galaxies down to H(AB)=26.5. The derived evolution of the global stellar mass density of galaxies is consistent with previous star formation rate density measurements over the observed range of redshifts. Beyond the observed range, maintaining consistency between the global stellar mass and the observed star formation rate suggests the epoch of galaxy formation was z=16.Comment: 18 pages, 3 figures, submitted to AJ. Data at: http://orca.phys.uvic.ca/~gwyn/MMM/nicmos.htm

Galaxy-Galaxy Lensing in the Hubble Deep Field: The Halo Tully-Fisher Relation at Intermediate Redshift

A tangential distortion of background source galaxies around foreground lens galaxies in the Hubble Deep Field is detected at the 99.3% confidence level. An important element of our analysis is the use of photometric redshifts to determine distances of lens and source galaxies and rest-frame B-band luminosities of the lens galaxies. The lens galaxy halos obey a Tully-Fisher relation between halo circular velocity and luminosity; the typical lens galaxy, at a redshift z = 0.6, has a circular velocity of 210 +/-40 km/s at M_B = -18.5, if q_0 = 0.5. Control tests, in which lens and source positions and source ellipticities are randomized, confirm the significance level of the detection quoted above. Furthermore, a marginal signal is also detected from an independent, fainter sample of source galaxies without photometric redshifts. Potential systematic effects, such as contamination by aligned satellite galaxies, the distortion of source shapes by the light of the foreground galaxies, PSF anisotropies, and contributions from mass distributed on the scale of galaxy groups are shown to be negligible. A comparison of our result with the local Tully-Fisher relation indicates that intermediate-redshift galaxies are fainter than local spirals by 1.0 +/- 0.6 B mag at a fixed circular velocity. This is consistent with some spectroscopic studies of the rotation curves of intermediate-redshift galaxies. This result suggests that the strong increase in the global luminosity density with redshift is dominated by evolution in the galaxy number density.Comment: Revised version with minor changes. 13 pages, 7 figures, LaTeX2e, uses emulateapj and multicol styles (included). Accepted by Ap

Correlation Between Phase Competition and the Nucleation of a Griffiths Phase in (La1-yPry)0.7Ca0.3Mn16/18O3

Detailed analyses of the temperature-dependent zero field ac susceptibility of prototypical phase-separated (La1-yPry)0.7Ca0.3Mn16/18O3, 0 < y < 1, reveal features consistent with the presence of a Griffiths phase (GP), viz., an inverse susceptibility characterized by power law with 0.05 < lamda < 0.33 as y decreases towards yc < 0.85. Beyond yc = 0.85, the GP is suppressed. These data, combined with previous neutron diffraction measurements, enable a phase diagram summarizing the evolution of the GP with composition to be constructed for this system; in particular, it shows that the disorder relevant for the establishment of such a phase is linked closely to the relative volume fractions of the phase separated antiferromagnetic and ferromagnetic components, even when the recently estimated double exchange (DE) linked percolation threshold is exceeded. The influence of electron-phonon coupling can also be seen through oxygen isotope effects.Comment: 4 page

ESCRT function in cytokinesis : location, dynamics and regulation by mitotic kinases

Mammalian cytokinesis proceeds by constriction of an actomyosin ring and furrow ingression, resulting in the formation of the midbody bridge connecting two daughter cells. At the centre of the midbody resides the Flemming body, a dense proteinaceous ring surrounding the interlocking ends of anti-parallel microtubule arrays. Abscission, the terminal step of cytokinesis, occurs near the Flemming body. A series of broad processes govern abscission: the initiation and stabilisation of the abscission zone, followed by microtubule severing and membrane scission—The latter mediated by the endosomal sorting complex required for transport (ESCRT) proteins. A key goal of cell and developmental biologists is to develop a clear understanding of the mechanisms that underpin abscission, and how the spatiotemporal coordination of these events with previous stages in cell division is accomplished. This article will focus on the function and dynamics of the ESCRT proteins in abscission and will review recent work, which has begun to explore how these complex protein assemblies are regulated by the cell cycle machinery