18 research outputs found
MMP Inhibition in Prostate Cancer
Matrix metalloproteinases (MMPs) play a significant role during the development and metastasis of prostate cancer (CaP). CaP cells secrete high levels of MMPs and low levels of endogenous MMP inhibitors (TIMPs), thus creating an excess balance of MMPs. Established CaP cell lines that express high levels of MMPs frequently metastasize to the bone and the lungs. Drugs such as Taxol and alendronate that reduce cell motility and calcium metabolism reduce bony metastasis of xenografted CaP tumors. We tested several synthetic, nontoxic inhibitors of MMPs that can be administered orally, including doxycycline (DC) and chemically modified tetracyclines (CMTs) on CaP cells in vitro and on a rat CaP model in vivo. Among several antiâMMP agents tested, CMTâ3 (6âdeoxy, 6âdemethyl,4âdeâdimethylamino tetracycline) showed highest activity against CaP cell invasion and cell proliferation. Micromolar concentration of CMTâ3 and DC inhibited both the secretion and activity of MMPs by CaP cells. When tested for in vivo efficacy in the Dunning rat CaP model by daily oral gavage, CMTâ3 and DC both reduced the lung metastases (> 50%). CMTâ3, but not DC, inhibited tumor incidence (55 ± 9%) and also reduced the tumor growth rate (27 ± 9.3%). More significantly, the drugs showed minimum systemic toxicity. Ongoing studies indicate that CMTâ3 may inhibit the skeletal metastases of CaP cells and delay the onset of paraplegia due to lumbar metastases. These preclinical studies provide the basis for clinical trials of CMTâ3 for the treatment of metastatic disease
Contrasted responses of two understorey species to direct and indirect effects of a canopy gap
Positive associations between adult trees and understorey species have been explained either by direct or indirect facilitation. We tested both models by comparing the performance of two understorey species with contrasted stress-tolerance abilities Galium odoratum and Deschampsia flexuosa. Individuals of both species were transplanted in the four combinations of two treatments (gap and removal of an herbaceous competitor, Molinia caerulea). Our experiment demonstrated that direct facilitation of adult trees may explain the restricted occurrence of the shade-demanding Galium within closed forest communities. In contrast, the shade-tolerant Deschampsia was subjected to additional competition within the forest, likely because adult trees had a higher negative effect on light availability and a similar negative effect on nitrogen availability within the forest than did Molinia in the gaps
Space Applications
Signals transmitted by global navigation satellite
system (GNSS) satellites are not confined to the
surface of the Earth but can likewise be used for
navigation in space. Satellites in low Earth orbits,
in particular, benefit from a similar signal strength
and experience a full-sky visibility. On the other
hand, the harsh space environment, long-term
reliability requirements and the high dynamics
of the host platform pose specific challenges to
the design and operation of space-borne GNSS
receivers. Despite these constraints, satellite manufacturers
and scientists have early on started to
exploit the benefits of GNSS technology. From the
first flight of a Global Positioning System (GPS) receiver
on Landsat-4, GNSS receivers have evolved
into indispensable and ubiquitous tools for navigation
and control of space vehicles.
Following a general introduction, the chapter
first describes the specific aspects of GNSS signal
tracking in space and highlights the technological
challenges of space-borne receiver design. Subsequently,
the use of GNSS for spacecraft navigation is
discussed taking into account both real-time navigation
and precise orbit determination. Relevant
algorithms and software tools are discussed and
the currently achieved performance is presented
based on actual missions and flight results.
A dedicated section is devoted to the use of spaceborne
GNSS for relative navigation of formation
flying satellites.
The chapter concludes with an outlook on
special applications such as spacecraft attitude
determination, GNSS tracking of ballistic vehicles
as well as GNSS radio science