1,787 research outputs found
Cell death and degeneration in the symbiotic dinoflagellates of the coral Stylophora pistillata during bleaching
Rising sea temperatures are increasing the incidences of mass coral bleaching (the dissociation
of the coral–algal symbiosis) and coral mortality. In this study, the effects of bleaching
(induced by elevated light and temperature) on the condition of symbiotic dinoflagellates (Symbiodinium
sp.) within the tissue of the hard coral Stylophora pistillata (Esper) were assessed using a suite
of techniques. Bleaching of S. pistillata was accompanied by declines in the maximum potential
quantum yield of photosynthesis (Fv/Fm, measured using pulse amplitude modulated [PAM] fluorometry),
an increase in the number of Sytox-green-stained algae (indicating compromised algal membrane
integrity and cell death), an increase in 2’,7’-dichlorodihydrofluroscein diacetate (H2DCFDA)-
stained algae (indicating increased oxidative stress), as well as ultrastructural changes (vacuolisation,
losses of chlorophyll, and an increase in accumulation bodies). Algae expelled from S. pistillata
exhibited a complete disorganisation of cellular contents; expelled cells contained only amorphous
material. In situ samples taken during a natural mass coral bleaching event on the Great Barrier Reef
in February 2002 also revealed a high number of Sytox-labelled algae cells in symbio. Dinoflagellate\ud
degeneration during bleaching seems to be similar to the changes resulting from senescence-phase
cell death in cultured algae. These data support a role for oxidative stress in the mechanism of coral
bleaching and highlight the importance of algal degeneration during the bleaching of a reef coral
A comparative study of methods for surface area and three-dimensional shape measurement of coral skeletons
The three-dimensional morphology and surface area of organisms such as reef-building corals is central to their biology. Consequently, being able to detect and measure this aspect of corals is critical to understanding their interactions with the surrounding environment. This study explores six different methods of three-dimensional shape and surface area measurements using the range of morphology associated with the Scleractinian corals: Goniopora tenuidens, Acropora intermedia, and Porites cylindrica. Wax dipping; foil wrapping; multi-station convergent photogrammetry that used the naturally occurring optical texture for conjugate point matching; stereo photogrammetry that used projected light to provide optical texture; a handheld laser scanner that employed two cameras and a structured light source; and X-ray computer tomography (CT) scanning were applied to each coral skeleton to determine the spatial resolution of surface detection as well as the accuracy of surface area estimate of each method. Compared with X-ray CT wax dipping provided the best estimate of the surface area of coral skeletons that had external corallites, regardless of morphological complexity. Foil wrapping consistently showed a large degree of error on all coral morphologies. The photogrammetry and laser-scanning solutions were effective only on corals with simple morphologies. The two techniques that used projected lighting were both subject to skeletal light scattering, caused by both gross morphology and meso-coral architecture and which degraded signal triangulation, but otherwise provided solutions with good spatial resolution. X-ray CT scanning provided the highest resolution surface area estimates, detecting surface features smaller than 1000 mu m(2)
The production, purification and crystallization of a pocilloporin pigment from a reef-forming coral
Reef-building corals contain fluorescent pigments termed pocilloporins that function by regulating the light environment of coral and acting as a photoprotectant in excessive sunlight. These pocilloporins are related to the monomeric green fluorescent protein and the tetrameric DsRed fluorescent proteins, which have widespread use as biotechnological tools. An intensely blue-coloured pocilloporin, termed Rtms5, was expressed in Escherichia coli, purified and crystallized. Rtms5 was shown to be tetrameric, with deep blue crystals that diffract to 2.2 Angstrom resolution and belong to space group I4(1)22. The colour of this pocilloporin was observed to be sensitive to pH and a yellow (pH 3.5) and a red form (pH 4.5) of Rtms5 were also crystallized. These crystals belong to space group P4(2)22 and diffract to 2.4 Angstrom resolution or better
The Nondeterministic Waiting Time Algorithm: A Review
We present briefly the Nondeterministic Waiting Time algorithm. Our technique
for the simulation of biochemical reaction networks has the ability to mimic
the Gillespie Algorithm for some networks and solutions to ordinary
differential equations for other networks, depending on the rules of the
system, the kinetic rates and numbers of molecules. We provide a full
description of the algorithm as well as specifics on its implementation. Some
results for two well-known models are reported. We have used the algorithm to
explore Fas-mediated apoptosis models in cancerous and HIV-1 infected T cells
Lie families: theory and applications
We analyze families of non-autonomous systems of first-order ordinary
differential equations admitting a common time-dependent superposition rule,
i.e., a time-dependent map expressing any solution of each of these systems in
terms of a generic set of particular solutions of the system and some
constants. We next study relations of these families, called Lie families, with
the theory of Lie and quasi-Lie systems and apply our theory to provide common
time-dependent superposition rules for certain Lie families.Comment: 23 pages, revised version to appear in J. Phys. A: Math. Theo
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