63 research outputs found
Aqueous TwoâPhase System Patterning of Microbubbles: Localized Induction of Apoptosis in Sonoporated Cells
Ultrasoundâdriven microbubbles produce mechanical forces that can disrupt cell membranes (sonoporation). However, it is difficult to control microbubble location with respect to cells. This lack of control leads to low sonoporation efficiencies and variable outcomes. In this study, aqueous twoâphase system (ATPS) droplets are used to localize microbubbles in select microâregions at the surface of living cells. This is achieved by stably partitioning microbubbles in dextran (DEX) droplets, deposited on living adherent cells in medium containing polyethylene glycol (PEG). The interfacial energy at the PEGâDEX interface overcomes microbubble buoyancy and prevents microbubbles from floating away from the cells. Spreading of the small DEX droplets retains microbubbles at the cell surface in defined lateral positions without the need for antibody or cellâbinding ligand conjugation. The patterned microbubbles are activated on a cell monolayer exposed to a broadly applied ultrasound field (center frequency 1.25 MHz, active element diameter 0.6 cm, pulse duration 8 ÎŒs or 30 s). This system enables efficient testing of different ultrasound conditions for their effects on sonoporationâmediated membrane disruption and cell viability. Regions of cells without patterned microbubbles show no injury or membrane disruption. In microbubble patterned regions, 8 ÎŒs ultrasound pulses (0.2â0.6 MPa) produce cell death that is primarily apoptotic. Ultrasoundâinduced apoptosis increases with higher extracellular calcium concentrations, with cells displaying all of the hallmarks of apoptosis including annexinV labeling, loss of mitochondrial membrane potential, caspase activation and changes in nuclear morphology. A new method is described for patterning microbubbles on cell monolayers to target ultrasound treatment to cells. This novel platform provides a controlled system for high throughput testing of the effects of ultrasoundâmediated cell membrane disruption on cell physiology. Using this patterning method, it is possible to induce apoptosis in select populations of cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99004/1/3420_ftp.pd
Effect of invader removal: pollinators stay but some native plants miss their new friend
Removal of invasive species often benefits
biological diversity allowing ecosystemsâ recovery.
However, it is important to assess the functional roles
that invaders may have established in their new areas
to avoid unexpected results from species elimination.
Invasive animal-pollinated plants may affect the
plantâpollination interactions by changing pollinator
availability and/or behaviour in the community. Thus,
removal of an invasive plant may have important
effects on pollinator community that may then be
reflected positive or negatively on the reproductive
success of native plants. The objective of this study
was to assess the effect of removing Oxalis pescaprae,
an invasive weed widely spread in the
Mediterranean basin, on plantâpollinator interactions
and on the reproductive success of co-flowering native
plants. For this, a disturbed area in central Portugal,
where this species is highly abundant, was selected.
Visitation rates, natural pollen loads, pollen tube
growth and natural fruit set of native plants were
compared in the presence of O. pes-caprae and after
manual removal of their flowers. Our results showed a
highly resilient pollination network but also revealed
some facilitative effects of O. pes-caprae on the
reproductive success of co-flowering native plants.
Reproductive success of the native plants seems to
depend not only on the number and diversity of floral
visitors, but also on their efficiency as pollinators. The
information provided on the effects of invasive species
on the sexual reproductive success of natives is
essential for adequate management of invaded areas.This work is financed by FEDER funds through the
COMPETE Program and by Portuguese Foundation for Science
and Technology (FCT) funds in the ambit of the project PTDC/
BIA-BIC/110824/2009, by CRUP AccžoËes Integradas Luso-
Espanholas 2010 with the project E10/10, by MCI-Programa de
InternacionalizacioÂŽn de la I ? D (PT2009-0068) and by the
Spanish DGICYT (CGL2009-10466), FEDER funds from the
European Union, and the Xunta de Galicia (INCITE09-
3103009PR). FCT also supported the work of S. Castro (FCT/
BPD/41200/2007) and J. Costa (CB/C05/2009/209; PTDC/
BIA-BIC/110824/2009). The work of V. Ferrero was supported
by the FundacioÂŽn RamoÂŽn Areces
Risks to pollinators and pollination from invasive alien species
Invasive alien species modify pollinator biodiversity and the services they provide that underpin ecosystem function and human well-being. Building on the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES) global assessment of pollinators and pollination, we synthesize current understanding of invasive alien impacts on pollinators and pollination. Invasive alien species create risks and opportunities for pollinator nutrition, re-organize species interactions to affect native pollination and community stability, and spread and select for virulent diseases. Risks are complex but substantial, and depend greatly on the ecological function and evolutionary history of both the invader and the recipient ecosystem. We highlight evolutionary implications for pollination from invasive alien species, and identify future research directions, key messages and options for decision-making
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