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Full-Text Articles in Cell Biology

Dorsoventral Boundary For Organizing Growth And Planar Polarity In The Drosophila Eye, Amit Singh, Janghoo Lim, Kwang-Wook Choi Jul 2015

Dorsoventral Boundary For Organizing Growth And Planar Polarity In The Drosophila Eye, Amit Singh, Janghoo Lim, Kwang-Wook Choi

Amit Singh

A fundamental feature of developing tissues and organs is generation of planar polarity of cells in an epithelium with respect to the body axis.

The Drosophila compound eye shows two-tier dorsoventral (DV) planar polarity. At the individual ommatidium level, the eight photoreceptors in each unit eye form a dorsoventrally asymmetric cluster. At the level of eye field, hundreds of ommatidia in the upper and lower halves of an eye are uniformly polarized dorsally or ventrally, respectively. This results in DV mirror symmetries about the equator. The uniform orientations of photoreceptor clusters over long distance in the eye field provide an ...


Deletion Of Aif1 But Not Of Yca1/Mca1 Protects Saccharomyces Cerevisiae And Candida Albicans Cells From Caspofungin-Induced Programmed Cell Death, Nicanor Austriaco, Christopher Chin, Faith Donaghey, Kathrine Helming, Morgan Mccarthy, Stephen Rogers Jul 2014

Deletion Of Aif1 But Not Of Yca1/Mca1 Protects Saccharomyces Cerevisiae And Candida Albicans Cells From Caspofungin-Induced Programmed Cell Death, Nicanor Austriaco, Christopher Chin, Faith Donaghey, Kathrine Helming, Morgan Mccarthy, Stephen Rogers

Rev. Nicanor Austriaco, O.P.

Caspofungin was the first member of a new class of antifungals called echinocandins to be approved by a drug regulatory authority. Like the other echinocandins, caspofungin blocks the synthesis of β(1,3)-D-glucan of the fungal cell wall by inhibiting the enzyme, β(1,3)-D-glucan synthase. Loss of β(1,3)-D-glucan leads to osmotic instability and cell death. However, the precise mechanism of cell death associated with the cytotoxicity of caspofungin was unclear. We now provide evidence that Saccharomyces cerevisiae cells cultured in media containing caspofungin manifest the classical hallmarks of programmed cell death (PCD) in yeast ...


Cortactin Regulates Cell Migration Via Activation Of N-Wasp, Jennifer Kowalski, C. Egile, S. Gil, S. Snapper, R. Li, S. Thomas Sep 2010

Cortactin Regulates Cell Migration Via Activation Of N-Wasp, Jennifer Kowalski, C. Egile, S. Gil, S. Snapper, R. Li, S. Thomas

Jennifer Kowalski

Cortactin is an actin-associated scaffolding protein that regulates cell migration. Amplification of the human gene, EMS1, has been detected in breast, head and neck tumors, where it correlates with increased invasiveness. Cortactin can regulate actin dynamics directly via its N-terminal half, which can bind and activate the Arp2/3 complex. The C-terminal portion of cortactin, however, is thought to have limited function in its regulation of the actin polymerization machinery. In this report, we identify a role for the cortactin C-terminus in regulating cell migration and, more specifically, actin dynamics. Overexpression of either full-length cortactin or cortactin C-terminus is sufficient ...


Microfluidics-Integrated Time-Lapse Imaging For Analysis Of Cellular Dynamics, Dirk Albrecht, Gregory Underhill, Joshua Resnikoff, Avital Mendelson, Sangeeta Bhatia, Jagesh Shah May 2010

Microfluidics-Integrated Time-Lapse Imaging For Analysis Of Cellular Dynamics, Dirk Albrecht, Gregory Underhill, Joshua Resnikoff, Avital Mendelson, Sangeeta Bhatia, Jagesh Shah

Dirk R. Albrecht

An understanding of the mechanisms regulating cellular responses has recently been augmented by innovations enabling the observation of phenotypes at high spatio-temporal resolution. Technologies such as microfluidics have sought to expand the throughput of these methods, although assimilation with advanced imaging strategies has been limited. Here, we describe the pairing of high resolution time-lapse imaging with microfluidic multiplexing for the analysis of cellular dynamics, utilizing a design selected for facile fabrication and operation, and integration with microscopy instrumentation. This modular, medium-throughput platform enables the long-term imaging of living cells at high numerical aperture (via oil immersion) by using a conserved ...


Life History, Sexual Dimorphism And 'Ornamental' Feathers In The Mesozoic Bird Confuciusornis Sanctus., Winfried S. Peters, Dieter Stefan Peters Sep 2009

Life History, Sexual Dimorphism And 'Ornamental' Feathers In The Mesozoic Bird Confuciusornis Sanctus., Winfried S. Peters, Dieter Stefan Peters

Winfried S. Peters

The life history of Confuciusornis sanctus is controversial. Recently, the species’ body size spectrum was claimed to contradict osteohistological evidence for a rapid, bird-like development. Moreover, sexual size dimorphism was rejected as an explanation for the observed bimodal size distribution since the presence of elongated rectrices, an assumed ‘male’ trait, was uncorrelated with size. However, this interpretation (i) fails to explain the size spectrum of C. sanctus which is trimodal rather than bimodal, (ii) requires implausible neonate masses and (iii) is not supported by analogy with sexual dimorphisms in modern birds, in which elongated central rectrices are mostly sex-independent. Available ...


Anisotropic Contraction In Forisomes: Simple Models Won't Fit, Winfried Peters, Michael Knoblauch, Stephen Warmann, William Pickard, Amy Shen Mar 2008

Anisotropic Contraction In Forisomes: Simple Models Won't Fit, Winfried Peters, Michael Knoblauch, Stephen Warmann, William Pickard, Amy Shen

Winfried S. Peters

Forisomes are ATP-independent, Ca2+-driven contractile protein bodies acting as reversible valves in the phloem of plants of the legume family. Forisome contraction is anisotropic, as shrinkage in length is associated with radial expansion and vice versa. To test the hypothesis that changes in length and width are causally related, we monitored Ca2+- and pH-dependent deformations in the exceptionally large forisomes of Canavalia gladiata by high-speed photography, and computed time-courses of derived geometric parameters (including volume and surface area). Soybean forisomes, which in the resting state resemble those of Canavalia geometrically but have less than 2% of the volume, were ...


Tailed Forisomes Of Canavalia Gladiata: A New Model To Study Ca2+-Driven Protein Contractility, Winfried Peters, Michael Knoblauch, Stephen Warmann, Reinhard Schnetter, Amy Shen, William Pickard Jun 2007

Tailed Forisomes Of Canavalia Gladiata: A New Model To Study Ca2+-Driven Protein Contractility, Winfried Peters, Michael Knoblauch, Stephen Warmann, Reinhard Schnetter, Amy Shen, William Pickard

Winfried S. Peters

Background and Aims Forisomes are Ca2+-dependent contractile protein bodies that form reversible plugs in sieve tubes of faboid legumes. Previous work employed Vicia faba forisomes, a not entirely unproblematic experimental system. The aim of this study was to seek to establish a superior model to study these intriguing actuators.
Methods Existing isolation procedures were modified to study the exceptionally large, tailed forisomes of Canavalia gladiata by differential interference contrast microscopy in vitro. To analyse contraction/expansion kinetics quantitatively, a geometric model was devised which enabled the computation of time-courses of derived parameters such as forisome volume from simple parameters ...


Reversible Birefringence Suggests A Role For Molecular Self-Assembly In Forisome Contractility, Winfried Peters, Reinhard Schnetter, Michael Knoblauch Apr 2007

Reversible Birefringence Suggests A Role For Molecular Self-Assembly In Forisome Contractility, Winfried Peters, Reinhard Schnetter, Michael Knoblauch

Winfried S. Peters

Forisomes are contractile protein bodies that control the effective diameter of the sieve elements of the faboid legumes by reversible, Ca2+-driven changes of shape. Forisomes consist of fibrils; we inferred from available electron-microscopical data (which necessarily provide images of fixed, non-functional forisomes) that a reversible assembly of ordered fibrillar arrays might be involved in the contractile mechanism. Here we examined functional forisomes isolated from Vicia faba L. by differential interference contrast microscopy and polarisation microscopy. We found them birefringent in the longitudinally expanded but not in the contracted state, showing ‘parallel extinction’ with the direction of vibration of the ...


Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters Nov 2004

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

The structural and functional analysis of biological macromolecules has reached a level of resolution that allows mechanistic interpretations of molecular action, giving rise to the view of enzymes as molecular machines. This machine analogy is not merely metaphorical, as bio-analogous molecular machines actually are being used as motors in the fields of nanotechnology and robotics. As the borderline between molecular cell biology and technology blurs, developments in the engineering and material sciences become increasingly instructive sources of models and concepts for biologists. In this review, we provide a – necessarily selective – summary of recent progress in the usage of biological and ...


Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters Apr 2004

Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. Motility of cell components in both animal and plant cells is mostly based on the movement of motor proteins along actin filaments or microtubules [Boal, 2002]. The dominance of ATP hydrolysis as the energy source for such movements is so complete, that modern textbooks define “motor proteins” as nucleoside triphosphate-dependent actuators [e.g., Alberts et al., 2002]. In only one known case, a reversible mechanism of cell motility is driven by the interaction of Ca2+ and the responsive protein(s). Some sessile ciliates control the effective length of their stalk ...


Changes Of Telomere Length Cause Reciprocal Changes In The Lifespan Of Mother Cells In Saccharomyces Cerevisiae, Father Nicanor Austriaco Sep 1997

Changes Of Telomere Length Cause Reciprocal Changes In The Lifespan Of Mother Cells In Saccharomyces Cerevisiae, Father Nicanor Austriaco

Rev. Nicanor Austriaco, O.P.

Budding yeast cells divide asymmetrically, giving rise to a mother and its daughter. Mother cells have a limited division potential, called their lifespan, which ends in proliferation-arrest and lysis. In this report we mutate telomerase in Saccharomyces cerevisiae to shorten telomeres and show that, rather than shortening lifespan, this leads to a significant extension in lifespan. This extension requires the product of the SIR3 gene, an essential component of the silencing machinery which binds to telomeres. In contrast, longer telomeres in a genotypically wild-type strain lead to a decrease in lifespan. These findings suggest that the length of telomeres dictates ...


Review: To Bud Until Death: The Genetics Of Aging In The Yeast, Saccharomyces, Father Nicanor Austriaco Dec 1995

Review: To Bud Until Death: The Genetics Of Aging In The Yeast, Saccharomyces, Father Nicanor Austriaco

Rev. Nicanor Austriaco, O.P.

Individual cells of the budding yeast, Saccharomyces cerevisiae, have a limited division capacity and undergo characteristicchanges as they senesce, primarily increasing both their cell size and cell cycle time. The mortality curve for ageing yeast cells can be described by the Gompertz equation, the classical definition for an ageing population. Recent work from several laboratories has demonstrated that genes can determine the yeast lifespan. Studies with the UTH genes have implicated changes in transcriptional silencing during yeast ageing, but the roles of the RAS2, LAG1 and PHBl genes in regulating yeast longevity are still unclear. What is becoming clearer, however ...


Pollination Of The Crown Imperial Fritillaria Imperialis By Great Tits Parus Major, Winfried S. Peters, Michael Pirl, Gerhard Gottsberger, Dieter Stefan Peters Feb 1995

Pollination Of The Crown Imperial Fritillaria Imperialis By Great Tits Parus Major, Winfried S. Peters, Michael Pirl, Gerhard Gottsberger, Dieter Stefan Peters

Winfried S. Peters

Visitations of flowers of the Crown Imperial by Great Tits at two different locations in Hessen, Germany, in 1990 and 1993 are described. The observations prove that flowers were visited because of the nectar; most likely pollination occurs during this visits. Similar reports from Europe are discussed. The significance of specific interactions including ecological generalists such as the Great Tit is considered in the context of the phylogenetic reconstruction of the development of co-adaptive syndroms.