scholarly journals Effects of cell morphology and attachment to a surface on the hydrodynamic performance of unicellular choanoflagellates

2019 ◽  
Vol 16 (150) ◽  
pp. 20180736 ◽  
Author(s):  
Hoa Nguyen ◽  
M. A. R. Koehl ◽  
Christian Oakes ◽  
Greg Bustamante ◽  
Lisa Fauci
Keyword(s):  
Aquatic Ecosystems ◽  
Cell Shape ◽  
Model System ◽  
Hydrodynamic Performance ◽  
Complex Life Cycle ◽  
Dispersal Stage ◽  
Salpingoeca Rosetta ◽  
Single Flagellum ◽  
Stalk Length ◽  
Sessile Cells

Choanoflagellates, eukaryotes that are important predators on bacteria in aquatic ecosystems, are closely related to animals and are used as a model system to study the evolution of animals from protozoan ancestors. The choanoflagellate Salpingoeca rosetta has a complex life cycle with different morphotypes, some unicellular and some multicellular. Here we use computational fluid dynamics to study the hydrodynamics of swimming and feeding by different unicellular stages of S. rosetta : a swimming cell with a collar of prey-capturing microvilli surrounding a single flagellum, a thecate cell attached to a surface and a dispersal-stage cell with a slender body, long flagellum and short collar. We show that a longer flagellum increases swimming speed, longer microvilli reduce speed and cell shape only affects speed when the collar is very short. The flux of prey-carrying water into the collar capture zone is greater for swimming than sessile cells, but this advantage decreases with collar size. Stalk length has little effect on flux for sessile cells. We show that ignoring the collar, as earlier models have done, overestimates flux and greatly overestimates the benefit to feeding performance of swimming versus being attached, and of a longer stalk for attached cells.

scholarly journals Genome editing enables reverse genetics of multicellular development in the choanoflagellate Salpingoeca rosetta

2020 ◽  
Author(s):  
David S. Booth ◽  
Nicole King
Keyword(s):  
Genome Editing ◽  
Reverse Genetics ◽  
Selectable Marker ◽  
Model System ◽  
Genetic Screen ◽  
Reverse Genetic ◽  
Genetic Screens ◽  
Multicellular Development ◽  
Forward Genetic Screen ◽  
Salpingoeca Rosetta

AbstractIn a previous study, we established a forward genetic screen to identify genes required for multicellular development in the choanoflagellate, Salpingoeca rosetta (Levin et al., 2014). Yet, the paucity of reverse genetic tools for choanoflagellates has hampered direct tests of gene function and impeded the establishment of choanoflagellates as a model for reconstructing the origin of their closest living relatives, the animals. Here we establish CRISPR/Cas9-mediated genome editing in S. rosetta by engineering a selectable marker to enrich for edited cells. We then use genome editing to disrupt the coding sequence of a S. rosetta C-type lectin gene, rosetteless, and thereby demonstrate its necessity for multicellular rosette development. This work advances S. rosetta as a model system in which to investigate how genes identified from genetic screens and genomic surveys function in choanoflagellates and evolved as critical regulators of animal biology.

scholarly journals Investigation of the role of calpain as a stimulus-response mediator in human platelets using new synthetic inhibitors

1991 ◽  
Vol 274 (2) ◽  
pp. 497-502 ◽  
Author(s):  
J Anagli ◽  
J Hagmann ◽  
E Shaw
Keyword(s):  
Cell Shape ◽  
Human Platelets ◽  
Model System ◽  
Actin Binding ◽  
Platelet Response ◽  
Calpain Activity ◽  
Stimulus Response ◽  
Affinity Labelling

A series of peptidyl diazomethanes and monofluoromethane with structures specific for calpain have been synthesized and tested for their ability to inhibit calpain activity in vivo, using human platelets as a model system. Calpain activity in vivo was determined by observing proteolysis of actin-binding protein and talin, two known substrates of calpain. Very potent inhibitors, which emerged from this study, were used to investigate the role of calpain in some platelet response processes. Our results show that calpain-mediated proteolysis in platelets is not an obligatory event leading to change of cell shape, adhesion to glass and spreading, aggregation and 5-hydroxytryptamine release. Two of the inhibitors were iodinated with 125I and used to radiolabel the enzyme in vivo. To our knowledge, this work also represents the first report describing the affinity labelling of calpain in human platelets using irreversible radioactive inhibitors.

scholarly journals Assessment of Toxicity of Coragen, an Insecticide, on Aquatic Ecosystem Using Hydra as a Model

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Borgave Seema Sachin
Keyword(s):  
Aquatic Ecosystem ◽  
Aquatic Ecosystems ◽  
Large Scale ◽  
Environmental Issues ◽  
Model System ◽  
Aquatic Species ◽  
Long Run ◽  
Low Concentrations ◽  
Ability To Regenerate ◽  
Harmful Effects

Overuse of insecticides, without analyzing their harmful effects, can cause serious environmental issues. Coragen is a commonly used insecticide due to its broad range activity. In spite of enormous use, there are hardly any reports on the effects of coragen on non-target aquatic species and thus the environmental risk of coragen to aquatic ecosystem is underestimated. The present study was carried out to evaluate the potential risk of coragen on the water bodies and the life therein using hy dra, a fresh water simple diploblastic invertebrate, as the model system. Coragen was found to reduce the life expectancy of hydra along with the reduced ability to regenerate at various tried doses. The present study thus suggests precocious use of coragen due to its harmful effects on aquatic animals at v ery low concentrations also. The continued overuse of coragen may disturb the aquatic ecosystems at a large scale in long run.

scholarly journals Bombina variegata (Linnaeus, 1758) in rain pools in the Carpathian Mountains (Slovakia)

2020 ◽  
Vol 69 (2) ◽  
pp. 165-174
Author(s):  
Alexander Csanády ◽  
Jozef Oboňa ◽  
Silvia Duranková
Keyword(s):  
Life Cycle ◽  
Aquatic Ecosystems ◽  
Conservation Status ◽  
Chemical Compounds ◽  
Larval Period ◽  
Complex Life Cycle ◽  
Time Data ◽  
Carpathian Mountains ◽  
Factors Affecting ◽  
Bombina Variegata

Abstract Rain pools (pluviotelmata or puddles) are common, small and non-permanent aquatic ecosystems. Data on the use of rain pools by amphibian taxa in the Carpathian Mountains, especially in Slovakia, are rare. In this study we describe the occurrence of Bombina variegata (Linnaeus, 1758), which may use these small aquatic ecosystems as part of their complex life cycle or where they spend their larval period. The most important hydroperiodic factors affecting the vertebrate fauna were the volume and area of the rain pools, the presence (respectively the absence) of shade, water temperature, biotope structure and the presence of several chemical compounds (NO− 3, GH, KH, pH). This study confirms that micro-habitats, such as rain pools, may play an important role for suitable reproduction sites of B. variegata, as stated by several authors from the different countries and regions of its large distributional range. At the same time, data on the presence or absence of different taxa with important conservation status in the monitored habitat aid in the detection of species.

scholarly journals Genome editing enables reverse genetics of multicellular development in the choanoflagellate Salpingoeca rosetta

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
David S Booth ◽  
Nicole King
Keyword(s):  
Genome Editing ◽  
Reverse Genetics ◽  
Selectable Marker ◽  
Model System ◽  
Genetic Screen ◽  
Reverse Genetic ◽  
Genetic Screens ◽  
Multicellular Development ◽  
Forward Genetic Screen ◽  
Salpingoeca Rosetta

In a previous study, we established a forward genetic screen to identify genes required for multicellular development in the choanoflagellate, Salpingoeca rosetta (Levin et al., 2014). Yet, the paucity of reverse genetic tools for choanoflagellates has hampered direct tests of gene function and impeded the establishment of choanoflagellates as a model for reconstructing the origin of their closest living relatives, the animals. Here we establish CRISPR/Cas9-mediated genome editing in S. rosetta by engineering a selectable marker to enrich for edited cells. We then use genome editing to disrupt the coding sequence of a S. rosetta C-type lectin gene, rosetteless, and thereby demonstrate its necessity for multicellular rosette development. This work advances S. rosetta as a model system in which to investigate how genes identified from genetic screens and genomic surveys function in choanoflagellates and evolved as critical regulators of animal biology.

scholarly journals Oncogenic signaling alters cell shape and mechanics to facilitate cell division under confinement

2019 ◽  
Author(s):  
Helen K. Matthews ◽  
Sushila Ganguli ◽  
Katarzyna Plak ◽  
Anna V. Taubenberger ◽  
Matthieu Piel ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Cell Mechanics ◽  
Cell Shape ◽  
Model System ◽  
Mcf10a Cell ◽  
Erk Pathway ◽  
Oncogenic Signaling ◽  
Mitotic Entry ◽  
Oncogenic Ras ◽  
Signalling Cascade

When cells enter mitosis, they become spherical and mechanically stiffen. We used MCF10A cell lines as a model system in which to investigate the effect of induced oncogene expression on mitotic entry. We find that activation of oncogenic RasV12, for as little as five hours, changes the way cells divide. RasV12-dependent activation of the MEK-ERK signalling cascade alters acto-myosin contractility to enhance mitotic rounding. RasV12also affects cell mechanics, so that RasV12expressing cells are softer in interphase but stiffen more upon entry into mitosis. As a consequence, RasV12expression augments the ability of cells to round up and divide faithfully when confined underneath a stiff hydrogel. Conversely, inhibition of the Ras-ERK pathway reduces mitotic rounding under confinement, resulting in chromosome segregation defects. These data suggest a novel mechanism by which oncogenic Ras-ERK signalling can aid division in stiff environments like those found in tumours.

A Protozoan Model for Golgi-Associated Calcification

1971 ◽  
Vol 29 ◽  
pp. 332-333
Author(s):  
D. C. Williams ◽  
D. E. Outka
Keyword(s):  
Golgi Apparatus ◽  
Organic Matrix ◽  
Model System ◽  
Sequential Formation

Many studies have shown that the Golgi apparatus is involved in a variety of synthetic activities, and probably no Golgi product is more elaborate than the scales produced by various kinds of phytoflagellates. The formation of calcified scales (coccoliths, Fig. 1,2) of the coccolithophorid phytoflagellates provides a particularly interesting model system for the study of biological mineralization, and the sequential formation of Golgi products.The coccoliths of Hymenomonas carterae consist of a scale-like base (Fig. 2 and 4, b) with a highly structured calcified (CaCO3) rim composed of two distinct elements which alternate about the base periphery (Fig. 1 and 3, A, B). Each element is enveloped by a sheath-like organic matrix (Fig. 3; Fig. 4, m).

Existence of DNA in yeast microbodies

1978 ◽  
Vol 36 (2) ◽  
pp. 232-233
Author(s):  
Masako Osumi ◽  
Misuzu Nagano ◽  
Hiroko Kazama
Keyword(s):  
Catalase Activity ◽  
Buoyant Density ◽  
Model System ◽  
Contour Length ◽  
Native State ◽  
Normal Alkane ◽  
Remarkable Increase ◽  
Dna Molecule ◽  
Mitochondrial Dnas

We have found that microbodies appeared profusely together with a remarkable increase in catalase activity in normal alkane-grown cells of hydrocarbon-utilizing Candida yeasts, and that the microbodies multiplied by division in these cells. These features of Candida yeasts seem to provide a useful model system for studies on the biogenesis of the microbody. Subsequently, we have succeeded in isolation of Candida microbodies in an apparently native state, as judged biochemically and morphologically. The presence of DNA in the purified microbody fraction thus obtained was proved by the diphenylamine method. DNA molecule of about 15 urn in contour length was released from an isolated microbody. The physicochemical analyses of the microbody DNA revealed that its buoyant density differed from nuclear and mitochondrial DNAs. All these results lead us to the possibility that there is a novel type of DNA in microbodies.

The coprecipitation of Cr3P and Cr in Cu

1988 ◽  
Vol 46 ◽  
pp. 764-765
Author(s):  
M.J. Witcomb ◽  
U. Dahmen ◽  
K.H. Westmacott
Keyword(s):  
Orientation Relationship ◽  
Interface Structure ◽  
Model System ◽  
Relative Orientation ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Solution Treated ◽  
Small Needle ◽  
Diffraction Patterns ◽  
Interface Structures

Cu-Cr age-hardening alloys are of interest as a model system for the investigation of fcc/bcc interface structures. Several past studies have investigated the morphology and interface structure of Cr precipitates in a Cu matrix (1-3) and good success has been achieved in understanding the crystallography and strain contrast of small needle-shaped precipitates. The present study investigates the effect of small amounts of phosphorous on the precipitation behavior of Cu-Cr alloys.The same Cu-0.3% Cr alloy as was used in earlier work was rolled to a thickness of 150 μm, solution treated in vacuum at 1050°C for 1h followed by quenching and annealing for various times at 820 and 863°C.Two laths and their corresponding diffraction patterns in an alloy aged 2h at 820°C are shown in correct relative orientation in Fig. 1. To within the limit of accuracy of the diffraction patterns the orientation relationship was that of Kurdjumov-Sachs (KS), i.e. parallel close-packed planes and directions.

Membrane-associated microtubular areays induced in proximal myelinated processes of dorsal root ganglia by large doses of vitamin B6

1986 ◽  
Vol 44 ◽  
pp. 368-369
Author(s):  
V.J. Montpetit ◽  
S. Dancea ◽  
L. Tryphonas ◽  
D.F. Clapin
Keyword(s):  
Animal Model ◽  
Endoplasmic Reticulum ◽  
Dorsal Root Ganglia ◽  
Rough Endoplasmic Reticulum ◽  
Dorsal Root ◽  
Vitamin B6 ◽  
Morphological Changes ◽  
Model System ◽  
Sensory Nerves ◽  
Peripheral Sensory

Very large doses of pyridoxine (vitamin B6) are neurotoxic in humans, selectively affecting the peripheral sensory nerves. We have undertaken a study of the morphological and biochemical aspects of pyridoxine neurotoxicity in an animal model system. Early morphological changes in dorsal root ganglia (DRG) associated with pyridoxine megadoses include proliferation of neurofilaments, ribosomes, rough endoplasmic reticulum, and Golgi complexes. We present in this report evidence of the formation of unique aggregates of microtubules and membranes in the proximal processes of DRG which are induced by high levels of pyridoxine.

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